Merge tag 'io_uring-7.3-20261002' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linuxgrafted

Pull io_uring fixes from Jens Axboe:

 - Fix a task_work add use-after-free with SQPOLL.

   The sqpoll thread could pop and complete the last request while
   io_req_normal_work_add() was still looking at them after the mpscq
   push.

   Use the same approach as DEFER_TASKRUN to protect from that, holding
   an RCU read lock across the add, and have exit wait for an RCU grace
   period for SQPOLL rings as well.

 - CQE32 ring fixes: correct the free entry check for 32b CQEs, zero the
   big_cqe for aux CQEs, and only post the dummy skip CQE on CQE_MIXED
   rings

 - Mark the source filter table as COW when cloning bpf filters, so
   registering another filter on the source doesn't modify the shared
   table in place

 - Initialize the task context before running the BPF loop

 - Requeue zcrx multishot receives stopped by a local resource

 - End a TX_TIMESTAMP multishot cmd when the CQ is full (lollipopkit)

* tag 'io_uring-7.3-20261002' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux:
  io_uring: fix task_work add use-after-free with SQPOLL
  io_uring/cmd_net: end TX_TIMESTAMP multishot when the CQ is full
  io_uring/zcrx: requeue multishot receives stopped by a local resource
  io_uring: initialize task context before running the BPF loop
  io_uring: zero big_cqe for aux CQEs on CQE32 rings
  io_uring: fix free entry check for 32b CQEs on CQE32 rings
  io_uring: only post the dummy skip CQE on CQE_MIXED rings
  io_uring/bpf_filter: mark source as COW when cloning filters

1 files changed, 2118 insertions, 0 deletions

diff --git a/fs/exec.c b/fs/exec.c
new file mode 100644
index 000000000..a5269b5e0
--- /dev/null
+++ b/fs/exec.c
@@ -0,0 +1,2118 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/exec.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+/*
+ * #!-checking implemented by tytso.
+ */
+/*
+ * Demand-loading implemented 01.12.91 - no need to read anything but
+ * the header into memory. The inode of the executable is put into
+ * "current->executable", and page faults do the actual loading. Clean.
+ *
+ * Once more I can proudly say that linux stood up to being changed: it
+ * was less than 2 hours work to get demand-loading completely implemented.
+ *
+ * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
+ * current->executable is only used by the procfs.  This allows a dispatch
+ * table to check for several different types  of binary formats.  We keep
+ * trying until we recognize the file or we run out of supported binary
+ * formats.
+ */
+
+#include <linux/kernel_read_file.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/mm.h>
+#include <linux/stat.h>
+#include <linux/fcntl.h>
+#include <linux/futex.h>
+#include <linux/swap.h>
+#include <linux/string.h>
+#include <linux/init.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/coredump.h>
+#include <linux/sched/exec_state.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/numa_balancing.h>
+#include <linux/sched/task.h>
+#include <linux/pagemap.h>
+#include <linux/perf_event.h>
+#include <linux/highmem.h>
+#include <linux/spinlock.h>
+#include <linux/key.h>
+#include <linux/personality.h>
+#include <linux/binfmts.h>
+#include <linux/utsname.h>
+#include <linux/pid_namespace.h>
+#include <linux/module.h>
+#include <linux/namei.h>
+#include <linux/mount.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/tsacct_kern.h>
+#include <linux/cn_proc.h>
+#include <linux/audit.h>
+#include <linux/kmod.h>
+#include <linux/fsnotify.h>
+#include <linux/fs_struct.h>
+#include <linux/oom.h>
+#include <linux/compat.h>
+#include <linux/vmalloc.h>
+#include <linux/io_uring.h>
+#include <linux/syscall_user_dispatch.h>
+#include <linux/coredump.h>
+#include <linux/time_namespace.h>
+#include <linux/user_events.h>
+#include <linux/rseq.h>
+#include <linux/ksm.h>
+
+#include <linux/uaccess.h>
+#include <asm/mmu_context.h>
+#include <asm/tlb.h>
+
+#include <trace/events/task.h>
+#include "internal.h"
+
+#include <trace/events/sched.h>
+
+/* For vma exec functions. */
+#include "../mm/internal.h"
+
+static int bprm_creds_from_file(struct linux_binprm *bprm);
+
+int suid_dumpable = 0;
+
+static LIST_HEAD(formats);
+static DEFINE_RWLOCK(binfmt_lock);
+
+void __register_binfmt(struct linux_binfmt * fmt, int insert)
+{
+	write_lock(&binfmt_lock);
+	insert ? list_add(&fmt->lh, &formats) :
+		 list_add_tail(&fmt->lh, &formats);
+	write_unlock(&binfmt_lock);
+}
+
+EXPORT_SYMBOL(__register_binfmt);
+
+void unregister_binfmt(struct linux_binfmt * fmt)
+{
+	write_lock(&binfmt_lock);
+	list_del(&fmt->lh);
+	write_unlock(&binfmt_lock);
+}
+
+EXPORT_SYMBOL(unregister_binfmt);
+
+static inline void put_binfmt(struct linux_binfmt * fmt)
+{
+	module_put(fmt->module);
+}
+
+bool path_noexec(const struct path *path)
+{
+	/* If it's an anonymous inode make sure that we catch any shenanigans. */
+	VFS_WARN_ON_ONCE(IS_ANON_FILE(d_inode(path->dentry)) &&
+			 !(path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC));
+	return (path->mnt->mnt_flags & MNT_NOEXEC) ||
+	       (path->mnt->mnt_sb->s_iflags & SB_I_NOEXEC);
+}
+
+#ifdef CONFIG_MMU
+/*
+ * The nascent bprm->mm is not visible until exec_mmap() but it can
+ * use a lot of memory, account these pages in current->mm temporary
+ * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
+ * change the counter back via acct_arg_size(0).
+ */
+static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
+{
+	struct mm_struct *mm = current->mm;
+	long diff = (long)(pages - bprm->vma_pages);
+
+	if (!mm || !diff)
+		return;
+
+	bprm->vma_pages = pages;
+	add_mm_counter(mm, MM_ANONPAGES, diff);
+}
+
+static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
+		int write)
+{
+	struct page *page;
+	struct vm_area_struct *vma = bprm->vma;
+	struct mm_struct *mm = bprm->mm;
+	int ret;
+
+	/*
+	 * Avoid relying on expanding the stack down in GUP (which
+	 * does not work for STACK_GROWSUP anyway), and just do it
+	 * ahead of time.
+	 */
+	if (!mmap_read_lock_maybe_expand(mm, vma, pos, write))
+		return NULL;
+
+	/*
+	 * We are doing an exec().  'current' is the process
+	 * doing the exec and 'mm' is the new process's mm.
+	 */
+	ret = get_user_pages_remote(mm, pos, 1,
+			write ? FOLL_WRITE : 0,
+			&page, NULL);
+	mmap_read_unlock(mm);
+	if (ret <= 0)
+		return NULL;
+
+	if (write)
+		acct_arg_size(bprm, vma_pages(vma));
+
+	return page;
+}
+
+static void put_arg_page(struct page *page)
+{
+	put_page(page);
+}
+
+static void free_arg_pages(struct linux_binprm *bprm)
+{
+}
+
+static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
+		struct page *page)
+{
+	flush_cache_page(bprm->vma, pos, page_to_pfn(page));
+}
+
+static bool valid_arg_len(struct linux_binprm *bprm, long len)
+{
+	return len <= MAX_ARG_STRLEN;
+}
+
+#else
+
+static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
+{
+}
+
+static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
+		int write)
+{
+	struct page *page;
+
+	page = bprm->page[pos / PAGE_SIZE];
+	if (!page && write) {
+		page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
+		if (!page)
+			return NULL;
+		bprm->page[pos / PAGE_SIZE] = page;
+	}
+
+	return page;
+}
+
+static void put_arg_page(struct page *page)
+{
+}
+
+static void free_arg_page(struct linux_binprm *bprm, int i)
+{
+	if (bprm->page[i]) {
+		__free_page(bprm->page[i]);
+		bprm->page[i] = NULL;
+	}
+}
+
+static void free_arg_pages(struct linux_binprm *bprm)
+{
+	int i;
+
+	for (i = 0; i < MAX_ARG_PAGES; i++)
+		free_arg_page(bprm, i);
+}
+
+static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
+		struct page *page)
+{
+}
+
+static bool valid_arg_len(struct linux_binprm *bprm, long len)
+{
+	return len <= bprm->p;
+}
+
+#endif /* CONFIG_MMU */
+
+/*
+ * Create a new mm_struct and populate it with a temporary stack
+ * vm_area_struct.  We don't have enough context at this point to set the stack
+ * flags, permissions, and offset, so we use temporary values.  We'll update
+ * them later in setup_arg_pages().
+ */
+static int bprm_mm_init(struct linux_binprm *bprm)
+{
+	int err;
+	struct mm_struct *mm = NULL;
+
+	bprm->mm = mm = mm_alloc();
+	err = -ENOMEM;
+	if (!mm)
+		goto err;
+
+	/* Staged for would_dump() narrowing; consumed by begin_new_exec(). */
+	bprm->user_ns = get_user_ns(current_user_ns());
+
+	/* Save current stack limit for all calculations made during exec. */
+	task_lock(current->group_leader);
+	bprm->rlim_stack = current->signal->rlim[RLIMIT_STACK];
+	task_unlock(current->group_leader);
+
+#ifndef CONFIG_MMU
+	bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
+#else
+	err = create_init_stack_vma(bprm->mm, &bprm->vma, &bprm->p);
+	if (err)
+		goto err;
+#endif
+
+	return 0;
+
+err:
+	if (mm) {
+		bprm->mm = NULL;
+		mmdrop(mm);
+	}
+
+	return err;
+}
+
+struct user_arg_ptr {
+#ifdef CONFIG_COMPAT
+	bool is_compat;
+#endif
+	union {
+		const char __user *const __user *native;
+#ifdef CONFIG_COMPAT
+		const compat_uptr_t __user *compat;
+#endif
+	} ptr;
+};
+
+static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
+{
+	const char __user *native;
+
+#ifdef CONFIG_COMPAT
+	if (unlikely(argv.is_compat)) {
+		compat_uptr_t compat;
+
+		if (get_user(compat, argv.ptr.compat + nr))
+			return ERR_PTR(-EFAULT);
+
+		return compat_ptr(compat);
+	}
+#endif
+
+	if (get_user(native, argv.ptr.native + nr))
+		return ERR_PTR(-EFAULT);
+
+	return native;
+}
+
+/*
+ * count() counts the number of strings in array ARGV.
+ */
+static int count(struct user_arg_ptr argv, int max)
+{
+	int i = 0;
+
+	if (argv.ptr.native != NULL) {
+		for (;;) {
+			const char __user *p = get_user_arg_ptr(argv, i);
+
+			if (!p)
+				break;
+
+			if (IS_ERR(p))
+				return -EFAULT;
+
+			if (i >= max)
+				return -E2BIG;
+			++i;
+
+			if (fatal_signal_pending(current))
+				return -ERESTARTNOHAND;
+			cond_resched();
+		}
+	}
+	return i;
+}
+
+static int count_strings_kernel(const char *const *argv)
+{
+	int i;
+
+	if (!argv)
+		return 0;
+
+	for (i = 0; argv[i]; ++i) {
+		if (i >= MAX_ARG_STRINGS)
+			return -E2BIG;
+		if (fatal_signal_pending(current))
+			return -ERESTARTNOHAND;
+		cond_resched();
+	}
+	return i;
+}
+
+static inline int bprm_set_stack_limit(struct linux_binprm *bprm,
+				       unsigned long limit)
+{
+#ifdef CONFIG_MMU
+	/* Avoid a pathological bprm->p. */
+	if (bprm->p < limit)
+		return -E2BIG;
+	bprm->argmin = bprm->p - limit;
+#endif
+	return 0;
+}
+static inline bool bprm_hit_stack_limit(struct linux_binprm *bprm)
+{
+#ifdef CONFIG_MMU
+	return bprm->p < bprm->argmin;
+#else
+	return false;
+#endif
+}
+
+/*
+ * Calculate bprm->argmin from:
+ * - _STK_LIM
+ * - ARG_MAX
+ * - bprm->rlim_stack.rlim_cur
+ * - bprm->argc
+ * - bprm->envc
+ * - bprm->p
+ */
+static int bprm_stack_limits(struct linux_binprm *bprm)
+{
+	unsigned long limit, ptr_size;
+
+	/*
+	 * Limit to 1/4 of the max stack size or 3/4 of _STK_LIM
+	 * (whichever is smaller) for the argv+env strings.
+	 * This ensures that:
+	 *  - the remaining binfmt code will not run out of stack space,
+	 *  - the program will have a reasonable amount of stack left
+	 *    to work from.
+	 */
+	limit = _STK_LIM / 4 * 3;
+	limit = min(limit, bprm->rlim_stack.rlim_cur / 4);
+	/*
+	 * We've historically supported up to 32 pages (ARG_MAX)
+	 * of argument strings even with small stacks
+	 */
+	limit = max_t(unsigned long, limit, ARG_MAX);
+	/* Reject totally pathological counts. */
+	if (bprm->argc < 0 || bprm->envc < 0)
+		return -E2BIG;
+	/*
+	 * We must account for the size of all the argv and envp pointers to
+	 * the argv and envp strings, since they will also take up space in
+	 * the stack. They aren't stored until much later when we can't
+	 * signal to the parent that the child has run out of stack space.
+	 * Instead, calculate it here so it's possible to fail gracefully.
+	 *
+	 * In the case of argc = 0, make sure there is space for adding a
+	 * empty string (which will bump argc to 1), to ensure confused
+	 * userspace programs don't start processing from argv[1], thinking
+	 * argc can never be 0, to keep them from walking envp by accident.
+	 * See do_execveat_common().
+	 */
+	if (check_add_overflow(max(bprm->argc, 1), bprm->envc, &ptr_size) ||
+	    check_mul_overflow(ptr_size, sizeof(void *), &ptr_size))
+		return -E2BIG;
+	if (limit <= ptr_size)
+		return -E2BIG;
+	limit -= ptr_size;
+
+	return bprm_set_stack_limit(bprm, limit);
+}
+
+/*
+ * 'copy_strings()' copies argument/environment strings from the old
+ * processes's memory to the new process's stack.  The call to get_user_pages()
+ * ensures the destination page is created and not swapped out.
+ */
+static int copy_strings(int argc, struct user_arg_ptr argv,
+			struct linux_binprm *bprm)
+{
+	struct page *kmapped_page = NULL;
+	char *kaddr = NULL;
+	unsigned long kpos = 0;
+	int ret;
+
+	while (argc-- > 0) {
+		const char __user *str;
+		int len;
+		unsigned long pos;
+
+		ret = -EFAULT;
+		str = get_user_arg_ptr(argv, argc);
+		if (IS_ERR(str))
+			goto out;
+
+		len = strnlen_user(str, MAX_ARG_STRLEN);
+		if (!len)
+			goto out;
+
+		ret = -E2BIG;
+		if (!valid_arg_len(bprm, len))
+			goto out;
+
+		/* We're going to work our way backwards. */
+		pos = bprm->p;
+		str += len;
+		bprm->p -= len;
+		if (bprm_hit_stack_limit(bprm))
+			goto out;
+
+		while (len > 0) {
+			int offset, bytes_to_copy;
+
+			if (fatal_signal_pending(current)) {
+				ret = -ERESTARTNOHAND;
+				goto out;
+			}
+			cond_resched();
+
+			offset = pos % PAGE_SIZE;
+			if (offset == 0)
+				offset = PAGE_SIZE;
+
+			bytes_to_copy = offset;
+			if (bytes_to_copy > len)
+				bytes_to_copy = len;
+
+			offset -= bytes_to_copy;
+			pos -= bytes_to_copy;
+			str -= bytes_to_copy;
+			len -= bytes_to_copy;
+
+			if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
+				struct page *page;
+
+				page = get_arg_page(bprm, pos, 1);
+				if (!page) {
+					ret = -E2BIG;
+					goto out;
+				}
+
+				if (kmapped_page) {
+					flush_dcache_page(kmapped_page);
+					kunmap_local(kaddr);
+					put_arg_page(kmapped_page);
+				}
+				kmapped_page = page;
+				kaddr = kmap_local_page(kmapped_page);
+				kpos = pos & PAGE_MASK;
+				flush_arg_page(bprm, kpos, kmapped_page);
+			}
+			if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
+				ret = -EFAULT;
+				goto out;
+			}
+		}
+	}
+	ret = 0;
+out:
+	if (kmapped_page) {
+		flush_dcache_page(kmapped_page);
+		kunmap_local(kaddr);
+		put_arg_page(kmapped_page);
+	}
+	return ret;
+}
+
+/*
+ * Copy and argument/environment string from the kernel to the processes stack.
+ */
+int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
+{
+	int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
+	unsigned long pos = bprm->p;
+
+	if (len == 0)
+		return -EFAULT;
+	if (!valid_arg_len(bprm, len))
+		return -E2BIG;
+
+	/* We're going to work our way backwards. */
+	arg += len;
+	bprm->p -= len;
+	if (bprm_hit_stack_limit(bprm))
+		return -E2BIG;
+
+	while (len > 0) {
+		unsigned int bytes_to_copy = min(len,
+				min_not_zero(offset_in_page(pos), PAGE_SIZE));
+		struct page *page;
+
+		pos -= bytes_to_copy;
+		arg -= bytes_to_copy;
+		len -= bytes_to_copy;
+
+		page = get_arg_page(bprm, pos, 1);
+		if (!page)
+			return -E2BIG;
+		flush_arg_page(bprm, pos & PAGE_MASK, page);
+		memcpy_to_page(page, offset_in_page(pos), arg, bytes_to_copy);
+		put_arg_page(page);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(copy_string_kernel);
+
+static int copy_strings_kernel(int argc, const char *const *argv,
+			       struct linux_binprm *bprm)
+{
+	while (argc-- > 0) {
+		int ret = copy_string_kernel(argv[argc], bprm);
+		if (ret < 0)
+			return ret;
+		if (fatal_signal_pending(current))
+			return -ERESTARTNOHAND;
+		cond_resched();
+	}
+	return 0;
+}
+
+#ifdef CONFIG_MMU
+
+/*
+ * Finalizes the stack vm_area_struct. The flags and permissions are updated,
+ * the stack is optionally relocated, and some extra space is added.
+ */
+int setup_arg_pages(struct linux_binprm *bprm,
+		    unsigned long stack_top,
+		    int executable_stack)
+{
+	int ret;
+	unsigned long stack_shift;
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma = bprm->vma;
+	struct vm_area_struct *prev = NULL;
+	vm_flags_t vm_flags;
+	unsigned long stack_base;
+	unsigned long stack_size;
+	unsigned long stack_expand;
+	unsigned long rlim_stack;
+	struct mmu_gather tlb;
+	struct vma_iterator vmi;
+
+#ifdef CONFIG_STACK_GROWSUP
+	/* Limit stack size */
+	stack_base = bprm->rlim_stack.rlim_max;
+
+	stack_base = calc_max_stack_size(stack_base);
+
+	/* Add space for stack randomization. */
+	if (current->flags & PF_RANDOMIZE)
+		stack_base += (STACK_RND_MASK << PAGE_SHIFT);
+
+	/* Make sure we didn't let the argument array grow too large. */
+	if (vma->vm_end - vma->vm_start > stack_base)
+		return -ENOMEM;
+
+	stack_base = PAGE_ALIGN(stack_top - stack_base);
+
+	stack_shift = vma->vm_start - stack_base;
+	mm->arg_start = bprm->p - stack_shift;
+	bprm->p = vma->vm_end - stack_shift;
+#else
+	stack_top = arch_align_stack(stack_top);
+	stack_top = PAGE_ALIGN(stack_top);
+
+	if (unlikely(stack_top < mmap_min_addr) ||
+	    unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
+		return -ENOMEM;
+
+	stack_shift = vma->vm_end - stack_top;
+
+	bprm->p -= stack_shift;
+	mm->arg_start = bprm->p;
+#endif
+
+	bprm->exec -= stack_shift;
+
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
+
+	vm_flags = VM_STACK_FLAGS;
+
+	/*
+	 * Adjust stack execute permissions; explicitly enable for
+	 * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
+	 * (arch default) otherwise.
+	 */
+	if (unlikely(executable_stack == EXSTACK_ENABLE_X))
+		vm_flags |= VM_EXEC;
+	else if (executable_stack == EXSTACK_DISABLE_X)
+		vm_flags &= ~VM_EXEC;
+	vm_flags |= mm->def_flags;
+	vm_flags |= VM_STACK_INCOMPLETE_SETUP;
+
+	vma_iter_init(&vmi, mm, vma->vm_start);
+
+	tlb_gather_mmu(&tlb, mm);
+	ret = mprotect_fixup(&vmi, &tlb, vma, &prev, vma->vm_start, vma->vm_end,
+			vm_flags);
+	tlb_finish_mmu(&tlb);
+
+	if (ret)
+		goto out_unlock;
+	BUG_ON(prev != vma);
+
+	if (unlikely(vm_flags & VM_EXEC)) {
+		pr_warn_once("process '%pD4' started with executable stack\n",
+			     bprm->file);
+	}
+
+	/* Move stack pages down in memory. */
+	if (stack_shift) {
+		/*
+		 * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
+		 * the binfmt code determines where the new stack should reside, we shift it to
+		 * its final location.
+		 */
+		ret = relocate_vma_down(vma, stack_shift);
+		if (ret)
+			goto out_unlock;
+	}
+
+	/* mprotect_fixup is overkill to remove the temporary stack flags */
+	vm_flags_clear(vma, VM_STACK_INCOMPLETE_SETUP);
+
+	stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
+	stack_size = vma->vm_end - vma->vm_start;
+	/*
+	 * Align this down to a page boundary as expand_stack
+	 * will align it up.
+	 */
+	rlim_stack = bprm->rlim_stack.rlim_cur & PAGE_MASK;
+
+	stack_expand = min(rlim_stack, stack_size + stack_expand);
+
+#ifdef CONFIG_STACK_GROWSUP
+	stack_base = vma->vm_start + stack_expand;
+#else
+	stack_base = vma->vm_end - stack_expand;
+#endif
+	current->mm->start_stack = bprm->p;
+	ret = expand_stack_locked(vma, stack_base);
+	if (ret)
+		ret = -EFAULT;
+
+out_unlock:
+	mmap_write_unlock(mm);
+	return ret;
+}
+EXPORT_SYMBOL(setup_arg_pages);
+
+#else
+
+/*
+ * Transfer the program arguments and environment from the holding pages
+ * onto the stack. The provided stack pointer is adjusted accordingly.
+ */
+int transfer_args_to_stack(struct linux_binprm *bprm,
+			   unsigned long *sp_location)
+{
+	unsigned long index, stop, sp;
+	int ret = 0;
+
+	stop = bprm->p >> PAGE_SHIFT;
+	sp = *sp_location;
+
+	for (index = MAX_ARG_PAGES; index-- > stop; ) {
+		unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
+		char *src = kmap_local_page(bprm->page[index]) + offset;
+		sp -= PAGE_SIZE - offset;
+		if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
+			ret = -EFAULT;
+		kunmap_local(src);
+		if (ret)
+			goto out;
+	}
+
+	bprm->exec += *sp_location - MAX_ARG_PAGES * PAGE_SIZE;
+	*sp_location = sp;
+
+out:
+	return ret;
+}
+EXPORT_SYMBOL(transfer_args_to_stack);
+
+#endif /* CONFIG_MMU */
+
+/*
+ * On success, caller must call do_close_execat() on the returned
+ * struct file to close it.
+ */
+static struct file *do_open_execat(int fd, struct filename *name, int flags)
+{
+	int err;
+	struct file *file __free(fput) = NULL;
+	struct open_flags open_exec_flags = {
+		.open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
+		.acc_mode = MAY_EXEC,
+		.intent = LOOKUP_OPEN,
+		.lookup_flags = LOOKUP_FOLLOW,
+	};
+
+	if ((flags &
+	     ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH | AT_EXECVE_CHECK)) != 0)
+		return ERR_PTR(-EINVAL);
+	if (flags & AT_SYMLINK_NOFOLLOW)
+		open_exec_flags.lookup_flags &= ~LOOKUP_FOLLOW;
+
+	file = do_file_open(fd, name, &open_exec_flags);
+	if (IS_ERR(file))
+		return file;
+
+	if (path_noexec(&file->f_path))
+		return ERR_PTR(-EACCES);
+
+	/*
+	 * In the past the regular type check was here. It moved to may_open() in
+	 * 633fb6ac3980 ("exec: move S_ISREG() check earlier"). Since then it is
+	 * an invariant that all non-regular files error out before we get here.
+	 */
+	if (WARN_ON_ONCE(!S_ISREG(file_inode(file)->i_mode)))
+		return ERR_PTR(-EACCES);
+
+	err = exe_file_deny_write_access(file);
+	if (err)
+		return ERR_PTR(err);
+
+	return no_free_ptr(file);
+}
+
+/**
+ * open_exec - Open a path name for execution
+ *
+ * @name: path name to open with the intent of executing it.
+ *
+ * Returns ERR_PTR on failure or allocated struct file on success.
+ *
+ * As this is a wrapper for the internal do_open_execat(), callers
+ * must call exe_file_allow_write_access() before fput() on release. Also see
+ * do_close_execat().
+ */
+struct file *open_exec(const char *name)
+{
+	CLASS(filename_kernel, filename)(name);
+	return do_open_execat(AT_FDCWD, filename, 0);
+}
+EXPORT_SYMBOL(open_exec);
+
+#if defined(CONFIG_BINFMT_FLAT) || defined(CONFIG_BINFMT_ELF_FDPIC)
+ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
+{
+	ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
+	if (res > 0)
+		flush_icache_user_range(addr, addr + len);
+	return res;
+}
+EXPORT_SYMBOL(read_code);
+#endif
+
+/*
+ * Maps the mm_struct mm into the current task struct.
+ * On success, this function returns with exec_update_lock
+ * held for writing. The replaced address space is stashed in
+ * bprm->old_mm for setup_new_exec() to release outside the lock.
+ */
+static int exec_mmap(struct linux_binprm *bprm)
+{
+	struct task_exec_state *exec_state __free(put_task_exec_state) = NULL;
+	struct mm_struct *mm = bprm->mm;
+	struct task_struct *tsk;
+	struct mm_struct *old_mm, *active_mm;
+	int ret;
+
+	exec_state = alloc_task_exec_state(bprm->user_ns);
+	if (!exec_state)
+		return -ENOMEM;
+
+	/* Notify parent that we're no longer interested in the old VM */
+	tsk = current;
+	old_mm = current->mm;
+	/* Clean up futexes and release the mm */
+	mm_exit_exec_release(tsk, old_mm);
+
+	ret = down_write_killable(&tsk->signal->exec_update_lock);
+	if (ret)
+		return ret;
+
+	if (old_mm) {
+		/*
+		 * If there is a pending fatal signal perhaps a signal
+		 * whose default action is to create a coredump get
+		 * out and die instead of going through with the exec.
+		 */
+		ret = mmap_read_lock_killable(old_mm);
+		if (ret) {
+			up_write(&tsk->signal->exec_update_lock);
+			return ret;
+		}
+	}
+
+	task_lock(tsk);
+	membarrier_exec_mmap(mm);
+
+	local_irq_disable();
+	active_mm = tsk->active_mm;
+	tsk->active_mm = mm;
+	tsk->mm = mm;
+	sched_cache_exec_mmap(tsk, mm);
+	mm_init_cid(mm, tsk);
+	exec_state = task_exec_state_replace(tsk, exec_state);
+	/*
+	 * This prevents preemption while active_mm is being loaded and
+	 * it and mm are being updated, which could cause problems for
+	 * lazy tlb mm refcounting when these are updated by context
+	 * switches. Not all architectures can handle irqs off over
+	 * activate_mm yet.
+	 */
+	if (!IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
+		local_irq_enable();
+	activate_mm(active_mm, mm);
+	if (IS_ENABLED(CONFIG_ARCH_WANT_IRQS_OFF_ACTIVATE_MM))
+		local_irq_enable();
+	lru_gen_add_mm(mm);
+	task_unlock(tsk);
+	lru_gen_use_mm(mm);
+	if (old_mm) {
+		mmap_read_unlock(old_mm);
+		BUG_ON(active_mm != old_mm);
+		/* Defer teardown to setup_new_exec(), outside the exec locks. */
+		bprm->old_mm = old_mm;
+	} else {
+		mmdrop_lazy_tlb(active_mm);
+	}
+	futex_exec_done(tsk);
+	return 0;
+}
+
+/* Release the address space replaced by exec, outside the exec locks. */
+static void exec_mm_put_old(struct mm_struct *old_mm)
+{
+	setmax_mm_hiwater_rss(&current->signal->maxrss, old_mm);
+	mm_update_next_owner(old_mm);
+	mmput(old_mm);
+}
+
+static int de_thread(struct task_struct *tsk)
+{
+	struct signal_struct *sig = tsk->signal;
+	struct sighand_struct *oldsighand = tsk->sighand;
+	spinlock_t *lock = &oldsighand->siglock;
+
+	if (thread_group_empty(tsk))
+		goto no_thread_group;
+
+	/*
+	 * Kill all other threads in the thread group.
+	 */
+	spin_lock_irq(lock);
+	if ((sig->flags & SIGNAL_GROUP_EXIT) || sig->group_exec_task) {
+		/*
+		 * Another group action in progress, just
+		 * return so that the signal is processed.
+		 */
+		spin_unlock_irq(lock);
+		return -EAGAIN;
+	}
+
+	sig->group_exec_task = tsk;
+	sig->notify_count = zap_other_threads(tsk);
+	if (!thread_group_leader(tsk))
+		sig->notify_count--;
+
+	while (sig->notify_count) {
+		__set_current_state(TASK_KILLABLE);
+		spin_unlock_irq(lock);
+		schedule();
+		if (__fatal_signal_pending(tsk))
+			goto killed;
+		spin_lock_irq(lock);
+	}
+	spin_unlock_irq(lock);
+
+	/*
+	 * At this point all other threads have exited, all we have to
+	 * do is to wait for the thread group leader to become inactive,
+	 * and to assume its PID:
+	 */
+	if (!thread_group_leader(tsk)) {
+		struct task_struct *leader = tsk->group_leader;
+
+		for (;;) {
+			cgroup_threadgroup_change_begin(tsk);
+			write_lock_irq(&tasklist_lock);
+			/*
+			 * Do this under tasklist_lock to ensure that
+			 * exit_notify() can't miss ->group_exec_task
+			 */
+			sig->notify_count = -1;
+			if (likely(leader->exit_state))
+				break;
+			__set_current_state(TASK_KILLABLE);
+			write_unlock_irq(&tasklist_lock);
+			cgroup_threadgroup_change_end(tsk);
+			schedule();
+			if (__fatal_signal_pending(tsk))
+				goto killed;
+		}
+
+		/*
+		 * The only record we have of the real-time age of a
+		 * process, regardless of execs it's done, is start_time.
+		 * All the past CPU time is accumulated in signal_struct
+		 * from sister threads now dead.  But in this non-leader
+		 * exec, nothing survives from the original leader thread,
+		 * whose birth marks the true age of this process now.
+		 * When we take on its identity by switching to its PID, we
+		 * also take its birthdate (always earlier than our own).
+		 */
+		tsk->start_time = leader->start_time;
+		tsk->start_boottime = leader->start_boottime;
+
+		BUG_ON(!same_thread_group(leader, tsk));
+		/*
+		 * An exec() starts a new thread group with the
+		 * TGID of the previous thread group. Rehash the
+		 * two threads with a switched PID, and release
+		 * the former thread group leader:
+		 */
+
+		/* Become a process group leader with the old leader's pid.
+		 * The old leader becomes a thread of the this thread group.
+		 */
+		exchange_tids(tsk, leader);
+		transfer_pid(leader, tsk, PIDTYPE_TGID);
+		transfer_pid(leader, tsk, PIDTYPE_PGID);
+		transfer_pid(leader, tsk, PIDTYPE_SID);
+
+		list_replace_rcu(&leader->tasks, &tsk->tasks);
+		list_replace_init(&leader->sibling, &tsk->sibling);
+
+		tsk->group_leader = tsk;
+		leader->group_leader = tsk;
+
+		tsk->exit_signal = SIGCHLD;
+		leader->exit_signal = -1;
+
+		BUG_ON(leader->exit_state != EXIT_ZOMBIE);
+		leader->exit_state = EXIT_DEAD;
+		/*
+		 * We are going to release_task()->ptrace_unlink() silently,
+		 * the tracer can sleep in do_wait(). EXIT_DEAD guarantees
+		 * the tracer won't block again waiting for this thread.
+		 */
+		if (unlikely(leader->ptrace))
+			__wake_up_parent(leader, leader->parent);
+		write_unlock_irq(&tasklist_lock);
+		cgroup_threadgroup_change_end(tsk);
+
+		release_task(leader);
+	}
+
+	sig->group_exec_task = NULL;
+	sig->notify_count = 0;
+
+no_thread_group:
+	/* we have changed execution domain */
+	tsk->exit_signal = SIGCHLD;
+
+	BUG_ON(!thread_group_leader(tsk));
+	return 0;
+
+killed:
+	/* protects against exit_notify() and __exit_signal() */
+	read_lock(&tasklist_lock);
+	sig->group_exec_task = NULL;
+	sig->notify_count = 0;
+	read_unlock(&tasklist_lock);
+	return -EAGAIN;
+}
+
+
+/*
+ * This function makes sure the current process has its own signal table,
+ * so that flush_signal_handlers can later reset the handlers without
+ * disturbing other processes.  (Other processes might share the signal
+ * table via the CLONE_SIGHAND option to clone().)
+ */
+static int unshare_sighand(struct task_struct *me)
+{
+	struct sighand_struct *oldsighand = me->sighand;
+
+	if (refcount_read(&oldsighand->count) != 1) {
+		struct sighand_struct *newsighand;
+		/*
+		 * This ->sighand is shared with the CLONE_SIGHAND
+		 * but not CLONE_THREAD task, switch to the new one.
+		 */
+		newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
+		if (!newsighand)
+			return -ENOMEM;
+
+		refcount_set(&newsighand->count, 1);
+
+		write_lock_irq(&tasklist_lock);
+		spin_lock(&oldsighand->siglock);
+		memcpy(newsighand->action, oldsighand->action,
+		       sizeof(newsighand->action));
+		rcu_assign_pointer(me->sighand, newsighand);
+		spin_unlock(&oldsighand->siglock);
+		write_unlock_irq(&tasklist_lock);
+
+		__cleanup_sighand(oldsighand);
+	}
+	return 0;
+}
+
+/*
+ * This is unlocked -- the string will always be NUL-terminated, but
+ * may show overlapping contents if racing concurrent reads.
+ */
+void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec)
+{
+	size_t len = strnlen(buf, sizeof(tsk->comm) - 1);
+
+	trace_task_rename(tsk, buf);
+	memcpy(tsk->comm, buf, len);
+	memset(&tsk->comm[len], 0, sizeof(tsk->comm) - len);
+	perf_event_comm(tsk, exec);
+}
+
+/*
+ * The file the process presents as: its exe link and comm. A transparent
+ * dispatch presents as the binary, which is bprm->executable.
+ */
+static struct file *bprm_identity_file(const struct linux_binprm *bprm)
+{
+	if (bprm->interp_flags & BINPRM_FLAGS_TRANSPARENT_INTERP)
+		return bprm->executable;
+	return bprm->file;
+}
+
+static void posixtimer_exec(struct task_struct *me)
+{
+#ifdef CONFIG_POSIX_TIMERS
+	spin_lock_irq(&me->sighand->siglock);
+	posix_cpu_timers_exit(me);
+	spin_unlock_irq(&me->sighand->siglock);
+	exit_itimers(me);
+	flush_itimer_signals();
+#endif
+}
+
+/*
+ * Calling this is the point of no return. None of the failures will be
+ * seen by userspace since either the process is already taking a fatal
+ * signal (via de_thread() or coredump), or will have SEGV raised
+ * (after exec_mmap()) by search_binary_handler (see below).
+ */
+int begin_new_exec(struct linux_binprm * bprm)
+{
+	struct task_struct *me = current;
+	int retval;
+
+	/* A pending PT_INTERP substitution this format cannot consume. */
+	if (bprm->loader)
+		return -ENOEXEC;
+
+	/* Once we are committed compute the creds */
+	retval = bprm_creds_from_file(bprm);
+	if (retval)
+		return retval;
+
+	/*
+	 * This tracepoint marks the point before flushing the old exec where
+	 * the current task is still unchanged, but errors are fatal (point of
+	 * no return). The later "sched_process_exec" tracepoint is called after
+	 * the current task has successfully switched to the new exec.
+	 */
+	trace_sched_prepare_exec(current, bprm);
+
+	/*
+	 * Ensure all future errors are fatal.
+	 */
+	bprm->point_of_no_return = true;
+
+	/* Make this the only thread in the thread group */
+	retval = de_thread(me);
+	if (retval)
+		goto out;
+
+	/*
+	 * This must be done here to ensure that POSIX CPU timers which were
+	 * armed on the current task are dequeued from me::posix_cputimers.
+	 * Otherwise in case of a TID switch the deletion of the related POSIX
+	 * timer would not remove an enqueued timer because the TID lookup
+	 * of the old TID fails.
+	 */
+	posixtimer_exec(me);
+
+	/* see the comment in check_unsafe_exec() */
+	current->fs->in_exec = 0;
+	/*
+	 * Cancel any io_uring activity across execve
+	 */
+	io_uring_task_cancel();
+
+	/* Ensure the files table is not shared. */
+	retval = unshare_files();
+	if (retval)
+		goto out;
+
+	/*
+	 * We have to apply CLOEXEC before we change whether the process is
+	 * dumpable (in setup_new_exec) to avoid a race with a process in userspace
+	 * trying to access the should-be-closed file descriptors of a process
+	 * undergoing exec(2).
+	 *
+	 * This can block on filesystem ->flush() handlers, including waiting
+	 * for FUSE daemons, so do it before exec_mmap takes the
+	 * exec_update_lock.
+	 * This must happen after the point of no return, and after unsharing
+	 * the FD table.
+	 */
+	do_close_on_exec(me->files);
+
+	/*
+	 * Must be called _before_ exec_mmap() as bprm->mm is
+	 * not visible until then. Doing it here also ensures
+	 * we don't race against replace_mm_exe_file().
+	 */
+	retval = set_mm_exe_file(bprm->mm, bprm_identity_file(bprm));
+	if (retval)
+		goto out;
+
+	/* If the binary is not readable then enforce mm->dumpable=0 */
+	would_dump(bprm, bprm->file);
+	if (bprm->have_execfd)
+		would_dump(bprm, bprm->executable);
+
+	/*
+	 * Release all of the old mmap stuff
+	 */
+	acct_arg_size(bprm, 0);
+	retval = exec_mmap(bprm);
+	if (retval)
+		goto out;
+
+	bprm->mm = NULL;
+
+	retval = exec_task_namespaces();
+	if (retval)
+		goto out_unlock;
+
+	/*
+	 * Make the signal table private.
+	 */
+	retval = unshare_sighand(me);
+	if (retval)
+		goto out_unlock;
+
+	me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC |
+					PF_NOFREEZE | PF_NO_SETAFFINITY);
+	flush_thread();
+	me->personality &= ~bprm->per_clear;
+
+	clear_syscall_work_syscall_user_dispatch(me);
+
+	if (bprm->secureexec) {
+		/* Make sure parent cannot signal privileged process. */
+		me->pdeath_signal = 0;
+
+		/*
+		 * For secureexec, reset the stack limit to sane default to
+		 * avoid bad behavior from the prior rlimits. This has to
+		 * happen before arch_pick_mmap_layout(), which examines
+		 * RLIMIT_STACK, but after the point of no return to avoid
+		 * needing to clean up the change on failure.
+		 */
+		if (bprm->rlim_stack.rlim_cur > _STK_LIM)
+			bprm->rlim_stack.rlim_cur = _STK_LIM;
+	}
+
+	me->sas_ss_sp = me->sas_ss_size = 0;
+
+	/*
+	 * Figure out dumpability. Note that this checking only of current
+	 * is wrong, but userspace depends on it. This should be testing
+	 * bprm->secureexec instead.
+	 */
+	if (bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP ||
+	    !(uid_eq(current_euid(), current_uid()) &&
+	      gid_eq(current_egid(), current_gid())))
+		task_exec_state_set_dumpable(suid_dumpable);
+	else
+		task_exec_state_set_dumpable(TASK_DUMPABLE_OWNER);
+
+	perf_event_exec();
+
+	/*
+	 * If the original filename was empty, alloc_bprm() made up a path
+	 * that will probably not be useful to admins running ps or similar.
+	 * Let's fix it up to be something reasonable.
+	 */
+	if (bprm->comm_from_dentry) {
+		struct file *comm_file = bprm_identity_file(bprm);
+
+		/*
+		 * Hold RCU lock to keep the name from being freed behind our back.
+		 * Use acquire semantics to make sure the terminating NUL from
+		 * __d_alloc() is seen.
+		 *
+		 * Note, we're deliberately sloppy here. We don't need to care about
+		 * detecting a concurrent rename and just want a terminated name.
+		 */
+		rcu_read_lock();
+		__set_task_comm(me, smp_load_acquire(&comm_file->f_path.dentry->d_name.name),
+				true);
+		rcu_read_unlock();
+	} else {
+		__set_task_comm(me, kbasename(bprm->filename), true);
+	}
+
+	/* An exec changes our domain. We are no longer part of the thread
+	   group */
+	WRITE_ONCE(me->self_exec_id, me->self_exec_id + 1);
+	flush_signal_handlers(me, 0);
+
+	retval = set_cred_ucounts(bprm->cred);
+	if (retval < 0)
+		goto out_unlock;
+
+	/*
+	 * install the new credentials for this executable
+	 */
+	security_bprm_committing_creds(bprm);
+
+	commit_creds(bprm->cred);
+	bprm->cred = NULL;
+
+	/*
+	 * Disable monitoring for regular users
+	 * when executing setuid binaries. Must
+	 * wait until new credentials are committed
+	 * by commit_creds() above
+	 */
+	if (task_exec_state_get_dumpable(me) != TASK_DUMPABLE_OWNER)
+		perf_event_exit_task(me);
+	/*
+	 * cred_guard_mutex must be held at least to this point to prevent
+	 * ptrace_attach() from altering our determination of the task's
+	 * credentials; any time after this it may be unlocked.
+	 */
+	security_bprm_committed_creds(bprm);
+
+	/* Pass the opened binary to the interpreter. */
+	if (bprm->have_execfd) {
+		struct file *executable = bprm->executable;
+
+		/* mm->exe_file carries its own write denial now so drop it. */
+		exe_file_allow_write_access(executable);
+		bprm->executable = NULL;
+		retval = FD_ADD(0, executable);
+		if (retval < 0) {
+			/* The reference was not consumed. */
+			fput(executable);
+			goto out_unlock;
+		}
+		bprm->execfd = retval;
+	}
+	return 0;
+
+out_unlock:
+	up_write(&me->signal->exec_update_lock);
+	if (!bprm->cred)
+		mutex_unlock(&me->signal->cred_guard_mutex);
+
+out:
+	return retval;
+}
+EXPORT_SYMBOL(begin_new_exec);
+
+void would_dump(struct linux_binprm *bprm, struct file *file)
+{
+	struct inode *inode = file_inode(file);
+	struct mnt_idmap *idmap = file_mnt_idmap(file);
+	if (inode_permission(idmap, inode, MAY_READ) < 0) {
+		struct user_namespace *old, *user_ns;
+		bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
+
+		/* Ensure bprm->user_ns contains the executable. */
+		user_ns = old = bprm->user_ns;
+		while ((user_ns != &init_user_ns) &&
+		       !privileged_wrt_inode_uidgid(user_ns, idmap, inode))
+			user_ns = user_ns->parent;
+
+		if (old != user_ns) {
+			bprm->user_ns = get_user_ns(user_ns);
+			put_user_ns(old);
+		}
+	}
+}
+EXPORT_SYMBOL(would_dump);
+
+void setup_new_exec(struct linux_binprm * bprm)
+{
+	/* Setup things that can depend upon the personality */
+	struct task_struct *me = current;
+
+	arch_pick_mmap_layout(me->mm, &bprm->rlim_stack);
+
+	arch_setup_new_exec();
+
+	/* Set the new mm task size. We have to do that late because it may
+	 * depend on TIF_32BIT which is only updated in flush_thread() on
+	 * some architectures like powerpc
+	 */
+	me->mm->task_size = TASK_SIZE;
+	up_write(&me->signal->exec_update_lock);
+	mutex_unlock(&me->signal->cred_guard_mutex);
+
+	/* The exec locks are dropped: release the old address space now. */
+	if (bprm->old_mm) {
+		exec_mm_put_old(bprm->old_mm);
+		bprm->old_mm = NULL;
+	}
+}
+EXPORT_SYMBOL(setup_new_exec);
+
+/* Runs immediately before start_thread() takes over. */
+void finalize_exec(struct linux_binprm *bprm)
+{
+	/* Store any stack rlimit changes before starting thread. */
+	task_lock(current->group_leader);
+	current->signal->rlim[RLIMIT_STACK] = bprm->rlim_stack;
+	task_unlock(current->group_leader);
+}
+EXPORT_SYMBOL(finalize_exec);
+
+/*
+ * Prepare credentials and lock ->cred_guard_mutex.
+ * setup_new_exec() commits the new creds and drops the lock.
+ * Or, if exec fails before, free_bprm() should release ->cred
+ * and unlock.
+ */
+static int prepare_bprm_creds(struct linux_binprm *bprm)
+{
+	if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
+		return -ERESTARTNOINTR;
+
+	bprm->cred = prepare_exec_creds();
+	if (likely(bprm->cred))
+		return 0;
+
+	mutex_unlock(&current->signal->cred_guard_mutex);
+	return -ENOMEM;
+}
+
+/* Matches do_open_execat() */
+static void do_close_execat(struct file *file)
+{
+	if (!file)
+		return;
+	exe_file_allow_write_access(file);
+	fput(file);
+}
+
+/**
+ * bprm_open_interpreter - open the interpreter the binary asks for
+ * @bprm: binary that is being executed
+ * @path: the interpreter path named in the binary's PT_INTERP
+ *
+ * A binfmt_misc loader entry substitutes for the interpreter the binary
+ * names. Hand out the stashed substitute if there is one and open @path
+ * if there is not. The caller owns the reference either way and releases
+ * it like any other open_exec() one.
+ *
+ * Return: the interpreter on success, an ERR_PTR on failure
+ */
+struct file *bprm_open_interpreter(struct linux_binprm *bprm, const char *path)
+{
+	if (bprm->loader)
+		return no_free_ptr(bprm->loader);
+	return open_exec(path);
+}
+
+/**
+ * bprm_drop_loader - discard a PT_INTERP substitute that does not apply
+ * @bprm: binary that is being executed
+ *
+ * A binary without PT_INTERP has nothing to substitute for, so drop the
+ * override and let the binary load natively rather than have
+ * begin_new_exec() refuse it. A no-op once bprm_open_interpreter() took
+ * the substitute.
+ */
+void bprm_drop_loader(struct linux_binprm *bprm)
+{
+	do_close_execat(no_free_ptr(bprm->loader));
+}
+
+static void free_bprm(struct linux_binprm *bprm)
+{
+	if (bprm->mm) {
+		acct_arg_size(bprm, 0);
+		mmput(bprm->mm);
+	}
+	if (bprm->user_ns)
+		put_user_ns(bprm->user_ns);
+	free_arg_pages(bprm);
+	if (bprm->cred) {
+		/* in case exec fails before de_thread() succeeds */
+		current->fs->in_exec = 0;
+		mutex_unlock(&current->signal->cred_guard_mutex);
+		abort_creds(bprm->cred);
+	}
+	/* exec swapped the mm but failed before setup_new_exec() freed it */
+	if (bprm->old_mm)
+		exec_mm_put_old(bprm->old_mm);
+	/* An unconsumed PT_INTERP substitute from a binfmt_misc loader entry. */
+	bprm_drop_loader(bprm);
+	do_close_execat(bprm->file);
+	do_close_execat(bprm->executable);
+	/* If a binfmt changed the interp, free it. */
+	if (bprm->interp != bprm->filename)
+		kfree(bprm->interp);
+	kfree(bprm->bpf_interp);
+	if (bprm->bpf_interp_file)
+		fput(bprm->bpf_interp_file);
+	kfree(bprm->bpf_interp_arg);
+	kfree(bprm->fdpath);
+	kfree(bprm);
+}
+
+static struct linux_binprm *alloc_bprm(int fd, struct filename *filename, int flags)
+{
+	struct linux_binprm *bprm;
+	struct file *file;
+	int retval = -ENOMEM;
+
+	file = do_open_execat(fd, filename, flags);
+	if (IS_ERR(file))
+		return ERR_CAST(file);
+
+	bprm = kzalloc_obj(*bprm);
+	if (!bprm) {
+		do_close_execat(file);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	bprm->file = file;
+
+	if (fd == AT_FDCWD || filename->name[0] == '/') {
+		bprm->filename = filename->name;
+	} else {
+		if (filename->name[0] == '\0') {
+			bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d", fd);
+			bprm->comm_from_dentry = 1;
+		} else {
+			bprm->fdpath = kasprintf(GFP_KERNEL, "/dev/fd/%d/%s",
+						  fd, filename->name);
+		}
+		if (!bprm->fdpath)
+			goto out_free;
+
+		/*
+		 * Record that a name derived from an O_CLOEXEC fd will be
+		 * inaccessible after exec.  This allows the code in exec to
+		 * choose to fail when the executable is not mmaped into the
+		 * interpreter and an open file descriptor is not passed to
+		 * the interpreter.  This makes for a better user experience
+		 * than having the interpreter start and then immediately fail
+		 * when it finds the executable is inaccessible.
+		 */
+		if (get_close_on_exec(fd))
+			bprm->interp_flags |= BINPRM_FLAGS_PATH_INACCESSIBLE;
+
+		bprm->filename = bprm->fdpath;
+	}
+	bprm->interp = bprm->filename;
+
+	/*
+	 * At this point, security_file_open() has already been called (with
+	 * __FMODE_EXEC) and access control checks for AT_EXECVE_CHECK will
+	 * stop just after the security_bprm_creds_for_exec() call in
+	 * bprm_execve().  Indeed, the kernel should not try to parse the
+	 * content of the file with exec_binprm() nor change the calling
+	 * thread, which means that the following security functions will not
+	 * be called:
+	 * - security_bprm_check()
+	 * - security_bprm_creds_from_file()
+	 * - security_bprm_committing_creds()
+	 * - security_bprm_committed_creds()
+	 */
+	bprm->is_check = !!(flags & AT_EXECVE_CHECK);
+
+	retval = bprm_mm_init(bprm);
+	if (!retval)
+		return bprm;
+
+out_free:
+	free_bprm(bprm);
+	return ERR_PTR(retval);
+}
+
+DEFINE_CLASS(bprm, struct linux_binprm *, if (!IS_ERR(_T)) free_bprm(_T),
+	alloc_bprm(fd, name, flags), int fd, struct filename *name, int flags)
+
+int bprm_change_interp(const char *interp, struct linux_binprm *bprm)
+{
+	/* If a binfmt changed the interp, free it first. */
+	if (bprm->interp != bprm->filename)
+		kfree(bprm->interp);
+	bprm->interp = kstrdup(interp, GFP_KERNEL);
+	if (!bprm->interp)
+		return -ENOMEM;
+	return 0;
+}
+EXPORT_SYMBOL(bprm_change_interp);
+
+/*
+ * determine how safe it is to execute the proposed program
+ * - the caller must hold ->cred_guard_mutex to protect against
+ *   PTRACE_ATTACH or seccomp thread-sync
+ */
+static void check_unsafe_exec(struct linux_binprm *bprm)
+{
+	struct task_struct *p = current, *t;
+	unsigned n_fs;
+
+	if (p->ptrace)
+		bprm->unsafe |= LSM_UNSAFE_PTRACE;
+
+	/*
+	 * This isn't strictly necessary, but it makes it harder for LSMs to
+	 * mess up.
+	 */
+	if (task_no_new_privs(current))
+		bprm->unsafe |= LSM_UNSAFE_NO_NEW_PRIVS;
+
+	/*
+	 * If another task is sharing our fs, we cannot safely
+	 * suid exec because the differently privileged task
+	 * will be able to manipulate the current directory, etc.
+	 * It would be nice to force an unshare instead...
+	 *
+	 * Otherwise we set fs->in_exec = 1 to deny clone(CLONE_FS)
+	 * from another sub-thread until de_thread() succeeds, this
+	 * state is protected by cred_guard_mutex we hold.
+	 */
+	n_fs = 1;
+	read_seqlock_excl(&p->fs->seq);
+	rcu_read_lock();
+	for_other_threads(p, t) {
+		if (t->fs == p->fs)
+			n_fs++;
+	}
+	rcu_read_unlock();
+
+	/* "users" and "in_exec" locked for copy_fs() */
+	if (p->fs->users > n_fs)
+		bprm->unsafe |= LSM_UNSAFE_SHARE;
+	else
+		p->fs->in_exec = 1;
+	read_sequnlock_excl(&p->fs->seq);
+}
+
+static void bprm_fill_uid(struct linux_binprm *bprm, struct file *file)
+{
+	/* Handle suid and sgid on files */
+	struct mnt_idmap *idmap;
+	struct inode *inode = file_inode(file);
+	unsigned int mode;
+	vfsuid_t vfsuid;
+	vfsgid_t vfsgid;
+	int err;
+
+	if (!mnt_may_suid(file->f_path.mnt))
+		return;
+
+	if (task_no_new_privs(current))
+		return;
+
+	mode = READ_ONCE(inode->i_mode);
+	if (!(mode & (S_ISUID|S_ISGID)))
+		return;
+
+	idmap = file_mnt_idmap(file);
+
+	/* Be careful if suid/sgid is set */
+	inode_lock(inode);
+
+	/* Atomically reload and check mode/uid/gid now that lock held. */
+	mode = inode->i_mode;
+	vfsuid = i_uid_into_vfsuid(idmap, inode);
+	vfsgid = i_gid_into_vfsgid(idmap, inode);
+	err = inode_permission(idmap, inode, MAY_EXEC);
+	inode_unlock(inode);
+
+	/* Did the exec bit vanish out from under us? Give up. */
+	if (err)
+		return;
+
+	/* We ignore suid/sgid if there are no mappings for them in the ns */
+	if (!vfsuid_has_mapping(bprm->cred->user_ns, vfsuid) ||
+	    !vfsgid_has_mapping(bprm->cred->user_ns, vfsgid))
+		return;
+
+	if (mode & S_ISUID) {
+		bprm->per_clear |= PER_CLEAR_ON_SETID;
+		bprm->cred->euid = vfsuid_into_kuid(vfsuid);
+	}
+
+	if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
+		bprm->per_clear |= PER_CLEAR_ON_SETID;
+		bprm->cred->egid = vfsgid_into_kgid(vfsgid);
+	}
+}
+
+/*
+ * Compute brpm->cred based upon the final binary.
+ */
+static int bprm_creds_from_file(struct linux_binprm *bprm)
+{
+	/* Compute creds based on which file? */
+	struct file *file = bprm->execfd_creds ? bprm->executable : bprm->file;
+
+	bprm_fill_uid(bprm, file);
+	return security_bprm_creds_from_file(bprm, file);
+}
+
+/*
+ * Fill the binprm structure from the inode.
+ * Read the first BINPRM_BUF_SIZE bytes
+ *
+ * This may be called multiple times for binary chains (scripts for example).
+ */
+static int prepare_binprm(struct linux_binprm *bprm)
+{
+	loff_t pos = 0;
+
+	memset(bprm->buf, 0, BINPRM_BUF_SIZE);
+	return kernel_read(bprm->file, bprm->buf, BINPRM_BUF_SIZE, &pos);
+}
+
+/*
+ * Arguments are '\0' separated strings found at the location bprm->p
+ * points to; chop off the first by relocating brpm->p to right after
+ * the first '\0' encountered.
+ */
+int remove_arg_zero(struct linux_binprm *bprm)
+{
+	unsigned long offset;
+	char *kaddr;
+	struct page *page;
+
+	if (!bprm->argc)
+		return 0;
+
+	do {
+		offset = bprm->p & ~PAGE_MASK;
+		page = get_arg_page(bprm, bprm->p, 0);
+		if (!page)
+			return -EFAULT;
+		kaddr = kmap_local_page(page);
+
+		for (; offset < PAGE_SIZE && kaddr[offset];
+				offset++, bprm->p++)
+			;
+
+		kunmap_local(kaddr);
+		put_arg_page(page);
+	} while (offset == PAGE_SIZE);
+
+	bprm->p++;
+	bprm->argc--;
+
+	return 0;
+}
+EXPORT_SYMBOL(remove_arg_zero);
+
+/*
+ * cycle the list of binary formats handler, until one recognizes the image
+ */
+static int search_binary_handler(struct linux_binprm *bprm)
+{
+	struct linux_binfmt *fmt;
+	int retval;
+
+	retval = prepare_binprm(bprm);
+	if (retval < 0)
+		return retval;
+
+	retval = security_bprm_check(bprm);
+	if (retval)
+		return retval;
+
+	read_lock(&binfmt_lock);
+	list_for_each_entry(fmt, &formats, lh) {
+		if (!try_module_get(fmt->module))
+			continue;
+		read_unlock(&binfmt_lock);
+
+		retval = fmt->load_binary(bprm);
+
+		read_lock(&binfmt_lock);
+		put_binfmt(fmt);
+		if (bprm->point_of_no_return || (retval != -ENOEXEC)) {
+			read_unlock(&binfmt_lock);
+			return retval;
+		}
+	}
+	read_unlock(&binfmt_lock);
+
+	return -ENOEXEC;
+}
+
+/* binfmt handlers will call back into begin_new_exec() on success. */
+static int exec_binprm(struct linux_binprm *bprm)
+{
+	pid_t old_pid, old_vpid;
+	int ret, depth;
+
+	/* Need to fetch pid before load_binary changes it */
+	old_pid = current->pid;
+	rcu_read_lock();
+	old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
+	rcu_read_unlock();
+
+	/* This allows 5 levels of binfmt rewrites before failing hard. */
+	for (depth = 0;; depth++) {
+		struct file *exec;
+		if (depth > 5)
+			return -ELOOP;
+
+		ret = search_binary_handler(bprm);
+		if (ret < 0)
+			return ret;
+		if (!bprm->interpreter)
+			break;
+
+		/* A stashed PT_INTERP substitute belonged to the replaced file. */
+		bprm_drop_loader(bprm);
+
+		exec = bprm->file;
+		bprm->file = bprm->interpreter;
+		bprm->interpreter = NULL;
+
+		if (unlikely(bprm->have_execfd)) {
+			if (bprm->executable) {
+				do_close_execat(exec);
+				return -ENOEXEC;
+			}
+			/* Kept for AT_EXECFD; the write denial rides along until hand-over. */
+			bprm->executable = exec;
+		} else {
+			do_close_execat(exec);
+		}
+	}
+
+	audit_bprm(bprm);
+	trace_sched_process_exec(current, old_pid, bprm);
+	ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
+	proc_exec_connector(current);
+	return 0;
+}
+
+static int bprm_execve(struct linux_binprm *bprm)
+{
+	int retval;
+
+	retval = prepare_bprm_creds(bprm);
+	if (retval)
+		return retval;
+
+	/*
+	 * Check for unsafe execution states before exec_binprm(), which
+	 * will call back into begin_new_exec(), into bprm_creds_from_file(),
+	 * where setuid-ness is evaluated.
+	 */
+	check_unsafe_exec(bprm);
+	current->in_execve = 1;
+	sched_mm_cid_before_execve(current);
+
+	sched_exec();
+
+	/* Set the unchanging part of bprm->cred */
+	retval = security_bprm_creds_for_exec(bprm);
+	if (retval || bprm->is_check)
+		goto out;
+
+	retval = exec_binprm(bprm);
+	if (retval < 0)
+		goto out;
+
+	sched_mm_cid_after_execve(current);
+	rseq_execve(current);
+	/* execve succeeded */
+	current->in_execve = 0;
+	user_events_execve(current);
+	acct_update_integrals(current);
+	task_numa_free(current, false);
+	return retval;
+
+out:
+	/*
+	 * If past the point of no return ensure the code never
+	 * returns to the userspace process.  Use an existing fatal
+	 * signal if present otherwise terminate the process with
+	 * SIGSEGV.
+	 */
+	if (bprm->point_of_no_return && !fatal_signal_pending(current))
+		force_fatal_sig(SIGSEGV);
+
+	sched_mm_cid_after_execve(current);
+	rseq_force_update();
+	current->in_execve = 0;
+
+	return retval;
+}
+
+static int do_execveat_common(int fd, struct filename *filename,
+			      struct user_arg_ptr argv,
+			      struct user_arg_ptr envp,
+			      int flags)
+{
+	int retval;
+
+	/*
+	 * We move the actual failure in case of RLIMIT_NPROC excess from
+	 * set*uid() to execve() because too many poorly written programs
+	 * don't check setuid() return code.  Here we additionally recheck
+	 * whether NPROC limit is still exceeded.
+	 */
+	if ((current->flags & PF_NPROC_EXCEEDED) &&
+	    is_rlimit_overlimit(current_ucounts(), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC)))
+		return -EAGAIN;
+
+	/* We're below the limit (still or again), so we don't want to make
+	 * further execve() calls fail. */
+	current->flags &= ~PF_NPROC_EXCEEDED;
+
+	CLASS(bprm, bprm)(fd, filename, flags);
+	if (IS_ERR(bprm))
+		return PTR_ERR(bprm);
+
+	retval = count(argv, MAX_ARG_STRINGS);
+	if (retval < 0)
+		return retval;
+	bprm->argc = retval;
+
+	retval = count(envp, MAX_ARG_STRINGS);
+	if (retval < 0)
+		return retval;
+	bprm->envc = retval;
+
+	retval = bprm_stack_limits(bprm);
+	if (retval < 0)
+		return retval;
+
+	retval = copy_string_kernel(bprm->filename, bprm);
+	if (retval < 0)
+		return retval;
+	bprm->exec = bprm->p;
+
+	retval = copy_strings(bprm->envc, envp, bprm);
+	if (retval < 0)
+		return retval;
+
+	retval = copy_strings(bprm->argc, argv, bprm);
+	if (retval < 0)
+		return retval;
+
+	/*
+	 * When argv is empty, add an empty string ("") as argv[0] to
+	 * ensure confused userspace programs that start processing
+	 * from argv[1] won't end up walking envp. See also
+	 * bprm_stack_limits().
+	 */
+	if (bprm->argc == 0) {
+		retval = copy_string_kernel("", bprm);
+		if (retval < 0)
+			return retval;
+		bprm->argc = 1;
+
+		pr_warn_once("process '%s' launched '%s' with NULL argv: empty string added\n",
+			     current->comm, bprm->filename);
+	}
+
+	return bprm_execve(bprm);
+}
+
+int kernel_execve(const char *kernel_filename,
+		  const char *const *argv, const char *const *envp)
+{
+	int retval;
+
+	/* It is non-sense for kernel threads to call execve */
+	if (WARN_ON_ONCE(current->flags & PF_KTHREAD))
+		return -EINVAL;
+
+	CLASS(filename_kernel, filename)(kernel_filename);
+	CLASS(bprm, bprm)(AT_FDCWD, filename, 0);
+	if (IS_ERR(bprm))
+		return PTR_ERR(bprm);
+
+	retval = count_strings_kernel(argv);
+	if (WARN_ON_ONCE(retval == 0))
+		return -EINVAL;
+	if (retval < 0)
+		return retval;
+	bprm->argc = retval;
+
+	retval = count_strings_kernel(envp);
+	if (retval < 0)
+		return retval;
+	bprm->envc = retval;
+
+	retval = bprm_stack_limits(bprm);
+	if (retval < 0)
+		return retval;
+
+	retval = copy_string_kernel(bprm->filename, bprm);
+	if (retval < 0)
+		return retval;
+	bprm->exec = bprm->p;
+
+	retval = copy_strings_kernel(bprm->envc, envp, bprm);
+	if (retval < 0)
+		return retval;
+
+	retval = copy_strings_kernel(bprm->argc, argv, bprm);
+	if (retval < 0)
+		return retval;
+
+	return bprm_execve(bprm);
+}
+
+void set_binfmt(struct linux_binfmt *new)
+{
+	struct mm_struct *mm = current->mm;
+
+	if (mm->binfmt)
+		module_put(mm->binfmt->module);
+
+	mm->binfmt = new;
+	if (new)
+		__module_get(new->module);
+}
+EXPORT_SYMBOL(set_binfmt);
+
+static inline struct user_arg_ptr native_arg(const char __user *const __user *p)
+{
+	return (struct user_arg_ptr){.ptr.native = p};
+}
+
+SYSCALL_DEFINE3(execve,
+		const char __user *, filename,
+		const char __user *const __user *, argv,
+		const char __user *const __user *, envp)
+{
+	CLASS(filename, name)(filename);
+	return do_execveat_common(AT_FDCWD, name,
+				  native_arg(argv), native_arg(envp), 0);
+}
+
+SYSCALL_DEFINE5(execveat,
+		int, fd, const char __user *, filename,
+		const char __user *const __user *, argv,
+		const char __user *const __user *, envp,
+		int, flags)
+{
+	CLASS(filename_uflags, name)(filename, flags);
+	return do_execveat_common(fd, name,
+				  native_arg(argv), native_arg(envp), flags);
+}
+
+#ifdef CONFIG_COMPAT
+
+static inline struct user_arg_ptr compat_arg(const compat_uptr_t __user *p)
+{
+	return (struct user_arg_ptr){.is_compat = true, .ptr.compat = p};
+}
+
+COMPAT_SYSCALL_DEFINE3(execve, const char __user *, filename,
+	const compat_uptr_t __user *, argv,
+	const compat_uptr_t __user *, envp)
+{
+	CLASS(filename, name)(filename);
+	return do_execveat_common(AT_FDCWD, name,
+				  compat_arg(argv), compat_arg(envp), 0);
+}
+
+COMPAT_SYSCALL_DEFINE5(execveat, int, fd,
+		       const char __user *, filename,
+		       const compat_uptr_t __user *, argv,
+		       const compat_uptr_t __user *, envp,
+		       int,  flags)
+{
+	CLASS(filename_uflags, name)(filename, flags);
+	return do_execveat_common(fd, name,
+				  compat_arg(argv), compat_arg(envp), flags);
+}
+#endif
+
+#ifdef CONFIG_SYSCTL
+
+static int proc_dointvec_minmax_coredump(const struct ctl_table *table, int write,
+		void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int error, old = READ_ONCE(suid_dumpable);
+
+	error = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+	if (!error && write && (old != READ_ONCE(suid_dumpable)))
+		validate_coredump_safety();
+	return error;
+}
+
+static const struct ctl_table fs_exec_sysctls[] = {
+	{
+		.procname	= "suid_dumpable",
+		.data		= &suid_dumpable,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax_coredump,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_TWO,
+	},
+};
+
+static int __init init_fs_exec_sysctls(void)
+{
+	register_sysctl_init("fs", fs_exec_sysctls);
+	return 0;
+}
+
+fs_initcall(init_fs_exec_sysctls);
+#endif /* CONFIG_SYSCTL */
+
+#ifdef CONFIG_EXEC_KUNIT_TEST
+#include "tests/exec_kunit.c"
+#endif