x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 596 insertions, 0 deletions

diff --git a/fs/afs/file.c b/fs/afs/file.c
new file mode 100644
index 000000000..0467742bf
--- /dev/null
+++ b/fs/afs/file.c
@@ -0,0 +1,596 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* AFS filesystem file handling
+ *
+ * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/writeback.h>
+#include <linux/gfp.h>
+#include <linux/task_io_accounting_ops.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/netfs.h>
+#include <trace/events/netfs.h>
+#include "internal.h"
+
+static int afs_file_mmap_prepare(struct vm_area_desc *desc);
+
+static ssize_t afs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter);
+static ssize_t afs_file_splice_read(struct file *in, loff_t *ppos,
+				    struct pipe_inode_info *pipe,
+				    size_t len, unsigned int flags);
+static void afs_vm_open(struct vm_area_struct *area);
+static void afs_vm_close(struct vm_area_struct *area);
+static vm_fault_t afs_vm_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff);
+static int afs_mapped(unsigned long start, unsigned long end, pgoff_t pgoff,
+		      const struct file *file, void **vm_private_data);
+
+const struct file_operations afs_file_operations = {
+	.open		= afs_open,
+	.release	= afs_release,
+	.llseek		= generic_file_llseek,
+	.read_iter	= afs_file_read_iter,
+	.write_iter	= netfs_file_write_iter,
+	.mmap_prepare	= afs_file_mmap_prepare,
+	.splice_read	= afs_file_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.fsync		= afs_fsync,
+	.lock		= afs_lock,
+	.flock		= afs_flock,
+};
+
+const struct inode_operations afs_file_inode_operations = {
+	.getattr	= afs_getattr,
+	.setattr	= afs_setattr,
+	.permission	= afs_permission,
+};
+
+const struct address_space_operations afs_file_aops = {
+	.direct_IO	= noop_direct_IO,
+	.read_folio	= netfs_read_folio,
+	.readahead	= netfs_readahead,
+	.dirty_folio	= netfs_dirty_folio,
+	.release_folio	= netfs_release_folio,
+	.invalidate_folio = netfs_invalidate_folio,
+	.migrate_folio	= filemap_migrate_folio,
+	.writepages	= afs_writepages,
+};
+
+static const struct vm_operations_struct afs_vm_ops = {
+	.mapped		= afs_mapped,
+	.open		= afs_vm_open,
+	.close		= afs_vm_close,
+	.fault		= filemap_fault,
+	.map_pages	= afs_vm_map_pages,
+	.page_mkwrite	= afs_page_mkwrite,
+};
+
+/*
+ * Discard a pin on a writeback key.
+ */
+void afs_put_wb_key(struct afs_wb_key *wbk)
+{
+	if (wbk && refcount_dec_and_test(&wbk->usage)) {
+		key_put(wbk->key);
+		kfree(wbk);
+	}
+}
+
+/*
+ * Cache key for writeback.
+ */
+int afs_cache_wb_key(struct afs_vnode *vnode, struct afs_file *af)
+{
+	struct afs_wb_key *wbk, *p;
+
+	wbk = kzalloc_obj(struct afs_wb_key);
+	if (!wbk)
+		return -ENOMEM;
+	refcount_set(&wbk->usage, 2);
+	wbk->key = af->key;
+
+	spin_lock(&vnode->wb_lock);
+	list_for_each_entry(p, &vnode->wb_keys, vnode_link) {
+		if (p->key == wbk->key)
+			goto found;
+	}
+
+	key_get(wbk->key);
+	list_add_tail(&wbk->vnode_link, &vnode->wb_keys);
+	spin_unlock(&vnode->wb_lock);
+	af->wb = wbk;
+	return 0;
+
+found:
+	refcount_inc(&p->usage);
+	spin_unlock(&vnode->wb_lock);
+	af->wb = p;
+	kfree(wbk);
+	return 0;
+}
+
+/*
+ * open an AFS file or directory and attach a key to it
+ */
+int afs_open(struct inode *inode, struct file *file)
+{
+	struct afs_vnode *vnode = AFS_FS_I(inode);
+	struct afs_file *af;
+	struct key *key;
+	int ret;
+
+	_enter("{%llx:%llu},", vnode->fid.vid, vnode->fid.vnode);
+
+	key = afs_request_key(vnode->volume->cell);
+	if (IS_ERR(key)) {
+		ret = PTR_ERR(key);
+		goto error;
+	}
+
+	af = kzalloc_obj(*af);
+	if (!af) {
+		ret = -ENOMEM;
+		goto error_key;
+	}
+	af->key = key;
+
+	ret = afs_validate(vnode, key);
+	if (ret < 0)
+		goto error_af;
+
+	if (file->f_mode & FMODE_WRITE) {
+		ret = afs_cache_wb_key(vnode, af);
+		if (ret < 0)
+			goto error_af;
+	}
+
+	if (file->f_flags & O_TRUNC)
+		set_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
+
+	fscache_use_cookie(afs_vnode_cache(vnode), file->f_mode & FMODE_WRITE);
+
+	file->private_data = af;
+	_leave(" = 0");
+	return 0;
+
+error_af:
+	kfree(af);
+error_key:
+	key_put(key);
+error:
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * release an AFS file or directory and discard its key
+ */
+int afs_release(struct inode *inode, struct file *file)
+{
+	struct afs_vnode_cache_aux aux;
+	struct afs_vnode *vnode = AFS_FS_I(inode);
+	struct afs_file *af = file->private_data;
+	loff_t i_size;
+	int ret = 0;
+
+	_enter("{%llx:%llu},", vnode->fid.vid, vnode->fid.vnode);
+
+	if ((file->f_mode & FMODE_WRITE))
+		ret = vfs_fsync(file, 0);
+
+	file->private_data = NULL;
+	if (af->wb)
+		afs_put_wb_key(af->wb);
+
+	if ((file->f_mode & FMODE_WRITE)) {
+		i_size = i_size_read(&vnode->netfs.inode);
+		afs_set_cache_aux(vnode, &aux);
+		fscache_unuse_cookie(afs_vnode_cache(vnode), &aux, &i_size);
+	} else {
+		fscache_unuse_cookie(afs_vnode_cache(vnode), NULL, NULL);
+	}
+
+	key_put(af->key);
+	kfree(af);
+	afs_prune_wb_keys(vnode);
+	_leave(" = %d", ret);
+	return ret;
+}
+
+static void afs_fetch_data_notify(struct afs_operation *op)
+{
+	struct netfs_io_subrequest *subreq = op->fetch.subreq;
+
+	subreq->error = afs_op_error(op);
+	netfs_read_subreq_terminated(subreq);
+}
+
+static void afs_fetch_data_success(struct afs_operation *op)
+{
+	struct afs_vnode *vnode = op->file[0].vnode;
+
+	_enter("op=%08x", op->debug_id);
+	afs_vnode_commit_status(op, &op->file[0]);
+	afs_stat_v(vnode, n_fetches);
+	atomic_long_add(op->fetch.subreq->transferred, &op->net->n_fetch_bytes);
+	afs_fetch_data_notify(op);
+}
+
+static void afs_fetch_data_aborted(struct afs_operation *op)
+{
+	afs_check_for_remote_deletion(op);
+	afs_fetch_data_notify(op);
+}
+
+const struct afs_operation_ops afs_fetch_data_operation = {
+	.issue_afs_rpc	= afs_fs_fetch_data,
+	.issue_yfs_rpc	= yfs_fs_fetch_data,
+	.success	= afs_fetch_data_success,
+	.aborted	= afs_fetch_data_aborted,
+	.failed		= afs_fetch_data_notify,
+};
+
+static void afs_issue_read_call(struct afs_operation *op)
+{
+	op->call_responded = false;
+	op->call_error = 0;
+	op->call_abort_code = 0;
+	if (test_bit(AFS_SERVER_FL_IS_YFS, &op->server->flags))
+		yfs_fs_fetch_data(op);
+	else
+		afs_fs_fetch_data(op);
+}
+
+static void afs_end_read(struct afs_operation *op)
+{
+	if (op->call_responded && op->server)
+		set_bit(AFS_SERVER_FL_RESPONDING, &op->server->flags);
+
+	if (!afs_op_error(op))
+		afs_fetch_data_success(op);
+	else if (op->cumul_error.aborted)
+		afs_fetch_data_aborted(op);
+	else
+		afs_fetch_data_notify(op);
+
+	afs_end_vnode_operation(op);
+	afs_put_operation(op);
+}
+
+/*
+ * Perform I/O processing on an asynchronous call.  The work item carries a ref
+ * to the call struct that we either need to release or to pass on.
+ */
+static void afs_read_receive(struct afs_call *call)
+{
+	struct afs_operation *op = call->op;
+	enum afs_call_state state;
+
+	_enter("");
+
+	state = READ_ONCE(call->state);
+	if (state == AFS_CALL_COMPLETE)
+		return;
+	trace_afs_read_recv(op, call);
+
+	while (state < AFS_CALL_COMPLETE && READ_ONCE(call->need_attention)) {
+		WRITE_ONCE(call->need_attention, false);
+		afs_deliver_to_call(call);
+		state = READ_ONCE(call->state);
+	}
+
+	if (state < AFS_CALL_COMPLETE) {
+		netfs_read_subreq_progress(op->fetch.subreq);
+		if (rxrpc_kernel_check_life(call->net->socket, call->rxcall))
+			return;
+		/* rxrpc terminated the call. */
+		afs_set_call_complete(call, call->error, call->abort_code);
+	}
+
+	op->call_abort_code	= call->abort_code;
+	op->call_error		= call->error;
+	op->call_responded	= call->responded;
+	op->call		= NULL;
+	call->op		= NULL;
+	afs_put_call(call);
+
+	/* If the call failed, then we need to crank the server rotation
+	 * handle and try the next.
+	 */
+	if (afs_select_fileserver(op)) {
+		afs_issue_read_call(op);
+		return;
+	}
+
+	afs_end_read(op);
+}
+
+void afs_fetch_data_async_rx(struct work_struct *work)
+{
+	struct afs_call *call = container_of(work, struct afs_call, async_work);
+
+	afs_read_receive(call);
+	afs_put_call(call);
+}
+
+void afs_fetch_data_immediate_cancel(struct afs_call *call)
+{
+	if (call->async) {
+		afs_get_call(call, afs_call_trace_wake);
+		if (!queue_work(afs_async_calls, &call->async_work))
+			afs_deferred_put_call(call);
+		flush_work(&call->async_work);
+	}
+}
+
+/*
+ * Fetch file data from the volume.
+ */
+static void afs_issue_read(struct netfs_io_subrequest *subreq)
+{
+	struct afs_operation *op;
+	struct afs_vnode *vnode = AFS_FS_I(subreq->rreq->inode);
+	struct key *key = subreq->rreq->netfs_priv;
+
+	_enter("%s{%llx:%llu.%u},%x,,,",
+	       vnode->volume->name,
+	       vnode->fid.vid,
+	       vnode->fid.vnode,
+	       vnode->fid.unique,
+	       key_serial(key));
+
+	op = afs_alloc_operation(key, vnode->volume);
+	if (IS_ERR(op)) {
+		subreq->error = PTR_ERR(op);
+		netfs_read_subreq_terminated(subreq);
+		return;
+	}
+
+	afs_op_set_vnode(op, 0, vnode);
+
+	op->fetch.subreq = subreq;
+	op->ops		= &afs_fetch_data_operation;
+
+	trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
+
+	if (subreq->rreq->origin == NETFS_READAHEAD ||
+	    subreq->rreq->iocb) {
+		op->flags |= AFS_OPERATION_ASYNC;
+
+		if (!afs_begin_vnode_operation(op)) {
+			subreq->error = afs_put_operation(op);
+			netfs_read_subreq_terminated(subreq);
+			return;
+		}
+
+		if (!afs_select_fileserver(op)) {
+			afs_end_read(op);
+			return;
+		}
+
+		afs_issue_read_call(op);
+	} else {
+		afs_do_sync_operation(op);
+	}
+}
+
+static int afs_init_request(struct netfs_io_request *rreq, struct file *file)
+{
+	struct afs_vnode *vnode = AFS_FS_I(rreq->inode);
+
+	if (file)
+		rreq->netfs_priv = key_get(afs_file_key(file));
+	rreq->rsize = 256 * 1024;
+	rreq->wsize = 256 * 1024 * 1024;
+
+	switch (rreq->origin) {
+	case NETFS_READ_SINGLE:
+		if (!file) {
+			struct key *key = afs_request_key(vnode->volume->cell);
+
+			if (IS_ERR(key))
+				return PTR_ERR(key);
+			rreq->netfs_priv = key;
+		}
+		break;
+	case NETFS_WRITEBACK:
+	case NETFS_WRITETHROUGH:
+	case NETFS_UNBUFFERED_WRITE:
+	case NETFS_DIO_WRITE:
+		if (S_ISREG(rreq->inode->i_mode))
+			rreq->io_streams[0].avail = true;
+		break;
+	case NETFS_WRITEBACK_SINGLE:
+	default:
+		break;
+	}
+	return 0;
+}
+
+static int afs_check_write_begin(struct file *file, loff_t pos, unsigned len,
+				 struct folio **foliop, void **_fsdata)
+{
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+
+	return test_bit(AFS_VNODE_DELETED, &vnode->flags) ? -ESTALE : 0;
+}
+
+static void afs_free_request(struct netfs_io_request *rreq)
+{
+	key_put(rreq->netfs_priv);
+	afs_put_wb_key(rreq->netfs_priv2);
+}
+
+/*
+ * Set the file size and block count, taking ->cb_lock and ->i_lock to maintain
+ * coherency and prevent 64-bit tearing on 32-bit arches.
+ *
+ * Also, estimate the number of 512 bytes blocks used, rounded up to nearest 1K
+ * for consistency with other AFS clients.
+ */
+void afs_set_i_size(struct afs_vnode *vnode, loff_t new_i_size)
+{
+	struct inode *inode = &vnode->netfs.inode;
+	loff_t i_size;
+
+	write_seqlock(&vnode->cb_lock);
+	spin_lock(&inode->i_lock);
+	i_size = i_size_read(inode);
+	if (new_i_size > i_size) {
+		i_size_write(inode, new_i_size);
+		inode_set_bytes(inode, round_up(new_i_size, 1024));
+	}
+	spin_unlock(&inode->i_lock);
+	write_sequnlock(&vnode->cb_lock);
+	fscache_update_cookie(afs_vnode_cache(vnode), NULL, &new_i_size);
+}
+
+static void afs_update_i_size(struct inode *inode, loff_t new_i_size)
+{
+	afs_set_i_size(AFS_FS_I(inode), new_i_size);
+}
+
+static void afs_netfs_invalidate_cache(struct netfs_io_request *wreq)
+{
+	struct afs_vnode *vnode = AFS_FS_I(wreq->inode);
+
+	afs_invalidate_cache(vnode, 0);
+}
+
+const struct netfs_request_ops afs_req_ops = {
+	.init_request		= afs_init_request,
+	.free_request		= afs_free_request,
+	.check_write_begin	= afs_check_write_begin,
+	.issue_read		= afs_issue_read,
+	.update_i_size		= afs_update_i_size,
+	.invalidate_cache	= afs_netfs_invalidate_cache,
+	.begin_writeback	= afs_begin_writeback,
+	.prepare_write		= afs_prepare_write,
+	.issue_write		= afs_issue_write,
+	.retry_request		= afs_retry_request,
+};
+
+static void afs_add_open_mmap(struct afs_vnode *vnode)
+{
+	if (atomic_inc_return(&vnode->cb_nr_mmap) == 1) {
+		down_write(&vnode->volume->open_mmaps_lock);
+
+		if (list_empty(&vnode->cb_mmap_link))
+			list_add_tail(&vnode->cb_mmap_link, &vnode->volume->open_mmaps);
+
+		up_write(&vnode->volume->open_mmaps_lock);
+	}
+}
+
+static void afs_drop_open_mmap(struct afs_vnode *vnode)
+{
+	if (atomic_add_unless(&vnode->cb_nr_mmap, -1, 1))
+		return;
+
+	down_write(&vnode->volume->open_mmaps_lock);
+
+	read_seqlock_excl(&vnode->cb_lock);
+	// the only place where ->cb_nr_mmap may hit 0
+	// see __afs_break_callback() for the other side...
+	if (atomic_dec_and_test(&vnode->cb_nr_mmap))
+		list_del_init(&vnode->cb_mmap_link);
+	read_sequnlock_excl(&vnode->cb_lock);
+
+	up_write(&vnode->volume->open_mmaps_lock);
+	flush_work(&vnode->cb_work);
+}
+
+/*
+ * Handle setting up a memory mapping on an AFS file.
+ */
+static int afs_file_mmap_prepare(struct vm_area_desc *desc)
+{
+	int ret;
+
+	ret = generic_file_mmap_prepare(desc);
+	if (ret)
+		return ret;
+
+	desc->vm_ops = &afs_vm_ops;
+	return ret;
+}
+
+static int afs_mapped(unsigned long start, unsigned long end, pgoff_t pgoff,
+		      const struct file *file, void **vm_private_data)
+{
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+
+	afs_add_open_mmap(vnode);
+	return 0;
+}
+
+static void afs_vm_open(struct vm_area_struct *vma)
+{
+	struct file *file = vma->vm_file;
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+
+	afs_add_open_mmap(vnode);
+}
+
+static void afs_vm_close(struct vm_area_struct *vma)
+{
+	struct file *file = vma->vm_file;
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+
+	afs_drop_open_mmap(vnode);
+}
+
+static vm_fault_t afs_vm_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff)
+{
+	struct file *file = vmf->vma->vm_file;
+	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+
+	if (afs_check_validity(vnode))
+		return filemap_map_pages(vmf, start_pgoff, end_pgoff);
+	return 0;
+}
+
+static ssize_t afs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	struct afs_vnode *vnode = AFS_FS_I(inode);
+	struct afs_file *af = iocb->ki_filp->private_data;
+	ssize_t ret;
+
+	if (iocb->ki_flags & IOCB_DIRECT)
+		return netfs_unbuffered_read_iter(iocb, iter);
+
+	ret = netfs_start_io_read(inode);
+	if (ret < 0)
+		return ret;
+	ret = afs_validate(vnode, af->key);
+	if (ret == 0)
+		ret = filemap_read(iocb, iter, 0);
+	netfs_end_io_read(inode);
+	return ret;
+}
+
+static ssize_t afs_file_splice_read(struct file *in, loff_t *ppos,
+				    struct pipe_inode_info *pipe,
+				    size_t len, unsigned int flags)
+{
+	struct inode *inode = file_inode(in);
+	struct afs_vnode *vnode = AFS_FS_I(inode);
+	struct afs_file *af = in->private_data;
+	ssize_t ret;
+
+	ret = netfs_start_io_read(inode);
+	if (ret < 0)
+		return ret;
+	ret = afs_validate(vnode, af->key);
+	if (ret == 0)
+		ret = filemap_splice_read(in, ppos, pipe, len, flags);
+	netfs_end_io_read(inode);
+	return ret;
+}