Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted

Pull I3C updates from Alexandre Belloni:
 "A new driver this cycle, for the AMD AXI I3C controller.

  There are also new features such as IBI wakeup support, SETAASA device
  discovery and ACPI support for the the DAA methods, meaning we can now
  communicate with the SPD devices on DDR5 modules.

  New driver:
   - AMD AXI I3C master controller

  Subsystem:
   - I3C Common Command Code (CCC) handling improvements, especially
     around GET CCCs
   - SETAASA device discovery support
   - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
     well as I2C devices on I3C bus
   - IBI-based wakeup support

  Drivers:
   - dw: SETAASA support
   - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
     controller support, PIO queue management support for HCI v1.2
   - renesas: improve suspend to RAM support, add runtime PM support"

* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
  i3c: dw: reduce do_daa time if there's no client
  i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
  i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
  i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
  i3c: dw: rename "pclk" to "apb" to match dt-binding
  i3c: dw: make struct dw_i3c_cmd smaller
  i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
  i3c: renesas: Don't register devices when ENTDAA times out
  i3c: master: dw-i3c-master: fix OD timing for first broadcast
  i3c: mipi-i3c-hci: Advertise IBI wakeup capability
  i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
  i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
  i3c: master: Reject IBI requests from non-IBI-capable devices
  i3c: master: Add helper to query bus wakeup requirements
  i3c: master: Report wakeup events for IBIs
  i3c: master: Support IBI-based wakeup capability
  i3c: master: Fix potential UAF in i3c_device_match()
  i3c: master: Fix potential UAF in i3c_device_uevent()
  i3c: Make dev->desc locking assumptions explicit
  i3c: master: Fix use-after-free of master->this
  ...

1 files changed, 252 insertions, 0 deletions

diff --git a/fs/fs_struct.c b/fs/fs_struct.c
new file mode 100644
index 000000000..34699f3b6
--- /dev/null
+++ b/fs/fs_struct.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/export.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/fs.h>
+#include <linux/path.h>
+#include <linux/slab.h>
+#include <linux/fs_struct.h>
+#include <linux/init_task.h>
+#include "internal.h"
+#include "mount.h"
+
+/*
+ * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
+ * It can block.
+ */
+void set_fs_root(struct fs_struct *fs, const struct path *path)
+{
+	struct path old_root;
+
+	path_get(path);
+	write_seqlock(&fs->seq);
+	old_root = fs->root;
+	fs->root = *path;
+	write_sequnlock(&fs->seq);
+	if (old_root.dentry)
+		path_put(&old_root);
+}
+
+/*
+ * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
+ * It can block.
+ */
+void set_fs_pwd(struct fs_struct *fs, const struct path *path)
+{
+	struct path old_pwd;
+
+	path_get(path);
+	write_seqlock(&fs->seq);
+	old_pwd = fs->pwd;
+	fs->pwd = *path;
+	write_sequnlock(&fs->seq);
+
+	if (old_pwd.dentry)
+		path_put(&old_pwd);
+}
+
+static inline int replace_path(struct path *p, const struct path *old, const struct path *new)
+{
+	if (likely(p->dentry != old->dentry || p->mnt != old->mnt))
+		return 0;
+	*p = *new;
+	return 1;
+}
+
+void chroot_fs_refs(const struct path *old_root, const struct path *new_root)
+{
+	struct task_struct *g, *p;
+	struct fs_struct *fs;
+	int count = 0;
+
+	read_lock(&tasklist_lock);
+	for_each_process_thread(g, p) {
+		if (p->flags & (PF_KTHREAD | PF_EXITING | PF_DUMPCORE))
+			continue;
+
+		task_lock(p);
+		fs = p->real_fs;
+		if (fs) {
+			int hits = 0;
+			write_seqlock(&fs->seq);
+			hits += replace_path(&fs->root, old_root, new_root);
+			hits += replace_path(&fs->pwd, old_root, new_root);
+			while (hits--) {
+				count++;
+				path_get(new_root);
+			}
+			write_sequnlock(&fs->seq);
+		}
+		task_unlock(p);
+	}
+	read_unlock(&tasklist_lock);
+	while (count--)
+		path_put(old_root);
+}
+
+void free_fs_struct(struct fs_struct *fs)
+{
+	path_put(&fs->root);
+	path_put(&fs->pwd);
+	kmem_cache_free(fs_cachep, fs);
+}
+
+void exit_fs(struct task_struct *tsk)
+{
+	struct fs_struct *fs = tsk->real_fs;
+
+	if (fs) {
+		int kill;
+		task_lock(tsk);
+		read_seqlock_excl(&fs->seq);
+		tsk->real_fs = NULL;
+		tsk->fs = NULL;
+		kill = !--fs->users;
+		read_sequnlock_excl(&fs->seq);
+		task_unlock(tsk);
+		if (kill)
+			free_fs_struct(fs);
+	}
+}
+
+struct fs_struct *copy_fs_struct(struct fs_struct *old)
+{
+	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
+	/* We don't need to lock fs - think why ;-) */
+	if (fs) {
+		fs->users = 1;
+		fs->in_exec = 0;
+		seqlock_init(&fs->seq);
+		fs->umask = old->umask;
+
+		read_seqlock_excl(&old->seq);
+		fs->root = old->root;
+		path_get(&fs->root);
+		fs->pwd = old->pwd;
+		path_get(&fs->pwd);
+		read_sequnlock_excl(&old->seq);
+	}
+	return fs;
+}
+
+int unshare_fs_struct(void)
+{
+	struct fs_struct *fs = current->real_fs;
+	struct fs_struct *new_fs = copy_fs_struct(fs);
+	int kill;
+
+	if (!new_fs)
+		return -ENOMEM;
+
+	task_lock(current);
+	read_seqlock_excl(&fs->seq);
+	VFS_WARN_ON_ONCE(fs != current->fs);
+	kill = !--fs->users;
+	current->fs = new_fs;
+	current->real_fs = new_fs;
+	read_sequnlock_excl(&fs->seq);
+	task_unlock(current);
+
+	if (kill)
+		free_fs_struct(fs);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(unshare_fs_struct);
+
+/*
+ * PID 1 may choose to stop sharing fs_struct state with us.
+ * Either via unshare(CLONE_FS) or unshare(CLONE_NEWNS). Of
+ * course, PID 1 could have chosen to create arbitrary process
+ * trees that all share fs_struct state via CLONE_FS. This is a
+ * strong statement: We only care about PID 1 aka the thread-group
+ * leader so subthread's fs_struct state doesn't matter.
+ *
+ * PID 1 unsharing fs_struct state is a bug. PID 1 relies on
+ * various kthreads to be able to perform work based on its
+ * fs_struct state. Breaking that contract sucks for both sides.
+ * So just don't bother with extra work for this. No sane init
+ * system should ever do this.
+ *
+ * On older kernels if PID 1 unshared its filesystem state with us the
+ * kernel simply used the stale fs_struct state implicitly pinning
+ * anything that PID 1 had last used. Even if PID 1 might've moved on to
+ * some completely different fs_struct state and might've even unmounted
+ * the old root.
+ *
+ * This has hilarious consequences: Think continuing to dump coredump
+ * state into an implicitly pinned directory somewhere. Calling random
+ * binaries in the old rootfs via usermodehelpers.
+ *
+ * Be aggressive about this: We simply reject operating on stale
+ * fs_struct state by reverting to nullfs. Every kworker that does
+ * lookups after this point will fail. Every usermodehelper call will
+ * fail. Tough luck but let's be kind and emit a warning to userspace.
+ */
+static inline void validate_fs_switch(struct fs_struct *old_fs)
+{
+	might_sleep();
+
+	if (likely(current->pid != 1))
+		return;
+	/* @old_fs may be dangling but for comparison it's fine */
+	if (old_fs != userspace_init_fs)
+		return;
+	pr_warn("VFS: Pid 1 stopped sharing filesystem state\n");
+	set_fs_root(userspace_init_fs, &init_fs.root);
+	set_fs_pwd(userspace_init_fs, &init_fs.root);
+}
+
+struct fs_struct *switch_fs_struct(struct fs_struct *new_fs)
+{
+	struct fs_struct *fs;
+
+	scoped_guard(task_lock, current) {
+		fs = current->fs;
+		VFS_WARN_ON_ONCE(fs != current->real_fs);
+		read_seqlock_excl(&fs->seq);
+		current->fs = new_fs;
+		current->real_fs = new_fs;
+		if (--fs->users)
+			new_fs = NULL;
+		else
+			new_fs = fs;
+		read_sequnlock_excl(&fs->seq);
+	}
+
+	validate_fs_switch(fs);
+	return new_fs;
+}
+
+/* to be mentioned only in INIT_TASK */
+struct fs_struct init_fs = {
+	.users		= 1,
+	.seq		= __SEQLOCK_UNLOCKED(init_fs.seq),
+	.umask		= 0022,
+};
+
+struct fs_struct *userspace_init_fs __ro_after_init;
+EXPORT_SYMBOL_GPL(userspace_init_fs);
+
+void __init init_userspace_fs(void)
+{
+	struct mount *m;
+	struct path root;
+
+	/* Move PID 1 from nullfs into the initramfs. */
+	m = topmost_overmount(current->nsproxy->mnt_ns->root);
+	root.mnt = &m->mnt;
+	root.dentry = root.mnt->mnt_root;
+
+	VFS_WARN_ON_ONCE(current->pid != 1);
+
+	set_fs_root(current->fs, &root);
+	set_fs_pwd(current->fs, &root);
+
+	/* Hold a reference for the global pointer. */
+	read_seqlock_excl(&current->fs->seq);
+	current->fs->users++;
+	read_sequnlock_excl(&current->fs->seq);
+
+	userspace_init_fs = current->fs;
+}