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, 452 insertions, 0 deletions

diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
new file mode 100644
index 000000000..090ec60fb
--- /dev/null
+++ b/fs/ocfs2/acl.c
@@ -0,0 +1,452 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * acl.c
+ *
+ * Copyright (C) 2004, 2008 Oracle.  All rights reserved.
+ *
+ * CREDITS:
+ * Lots of code in this file is copy from linux/fs/ext3/acl.c.
+ * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/fs_struct.h>
+
+#include <cluster/masklog.h>
+
+#include "ocfs2.h"
+#include "alloc.h"
+#include "dlmglue.h"
+#include "file.h"
+#include "inode.h"
+#include "journal.h"
+#include "ocfs2_fs.h"
+
+#include "xattr.h"
+#include "acl.h"
+
+/*
+ * Convert from xattr value to acl struct.
+ */
+static struct posix_acl *ocfs2_acl_from_xattr(const void *value, size_t size)
+{
+	int n, count;
+	struct posix_acl *acl;
+
+	if (!value)
+		return NULL;
+	if (size < sizeof(struct posix_acl_entry))
+		return ERR_PTR(-EINVAL);
+
+	count = size / sizeof(struct posix_acl_entry);
+
+	acl = posix_acl_alloc(count, GFP_NOFS);
+	if (!acl)
+		return ERR_PTR(-ENOMEM);
+	for (n = 0; n < count; n++) {
+		struct ocfs2_acl_entry *entry =
+			(struct ocfs2_acl_entry *)value;
+
+		acl->a_entries[n].e_tag  = le16_to_cpu(entry->e_tag);
+		acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
+		switch(acl->a_entries[n].e_tag) {
+		case ACL_USER:
+			acl->a_entries[n].e_uid =
+				make_kuid(&init_user_ns,
+					  le32_to_cpu(entry->e_id));
+			break;
+		case ACL_GROUP:
+			acl->a_entries[n].e_gid =
+				make_kgid(&init_user_ns,
+					  le32_to_cpu(entry->e_id));
+			break;
+		default:
+			break;
+		}
+		value += sizeof(struct posix_acl_entry);
+
+	}
+	return acl;
+}
+
+/*
+ * Convert acl struct to xattr value.
+ */
+static void *ocfs2_acl_to_xattr(const struct posix_acl *acl, size_t *size)
+{
+	struct ocfs2_acl_entry *entry = NULL;
+	char *ocfs2_acl;
+	size_t n;
+
+	*size = acl->a_count * sizeof(struct posix_acl_entry);
+
+	ocfs2_acl = kmalloc(*size, GFP_NOFS);
+	if (!ocfs2_acl)
+		return ERR_PTR(-ENOMEM);
+
+	entry = (struct ocfs2_acl_entry *)ocfs2_acl;
+	for (n = 0; n < acl->a_count; n++, entry++) {
+		entry->e_tag  = cpu_to_le16(acl->a_entries[n].e_tag);
+		entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
+		switch(acl->a_entries[n].e_tag) {
+		case ACL_USER:
+			entry->e_id = cpu_to_le32(
+				from_kuid(&init_user_ns,
+					  acl->a_entries[n].e_uid));
+			break;
+		case ACL_GROUP:
+			entry->e_id = cpu_to_le32(
+				from_kgid(&init_user_ns,
+					  acl->a_entries[n].e_gid));
+			break;
+		default:
+			entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
+			break;
+		}
+	}
+	return ocfs2_acl;
+}
+
+static struct posix_acl *ocfs2_get_acl_nolock(struct inode *inode, int type,
+					      struct buffer_head *di_bh)
+{
+	int name_index;
+	char *value = NULL;
+	struct posix_acl *acl;
+	int retval;
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		name_index = OCFS2_XATTR_INDEX_POSIX_ACL_ACCESS;
+		break;
+	case ACL_TYPE_DEFAULT:
+		name_index = OCFS2_XATTR_INDEX_POSIX_ACL_DEFAULT;
+		break;
+	default:
+		return ERR_PTR(-EINVAL);
+	}
+
+	retval = ocfs2_xattr_get_nolock(inode, di_bh, name_index, "", NULL, 0);
+	if (retval > 0) {
+		value = kmalloc(retval, GFP_NOFS);
+		if (!value)
+			return ERR_PTR(-ENOMEM);
+		retval = ocfs2_xattr_get_nolock(inode, di_bh, name_index,
+						"", value, retval);
+	}
+
+	if (retval > 0)
+		acl = ocfs2_acl_from_xattr(value, retval);
+	else if (retval == -ENODATA || retval == 0)
+		acl = NULL;
+	else
+		acl = ERR_PTR(retval);
+
+	kfree(value);
+
+	return acl;
+}
+
+/*
+ * Helper function to set i_mode in memory and disk. Some call paths
+ * will not have di_bh or a journal handle to pass, in which case it
+ * will create it's own.
+ */
+static int ocfs2_acl_set_mode(struct inode *inode, struct buffer_head *di_bh,
+			      handle_t *handle, umode_t new_mode)
+{
+	int ret, commit_handle = 0;
+	struct ocfs2_dinode *di;
+
+	if (di_bh == NULL) {
+		ret = ocfs2_read_inode_block(inode, &di_bh);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+	} else
+		get_bh(di_bh);
+
+	if (handle == NULL) {
+		handle = ocfs2_start_trans(OCFS2_SB(inode->i_sb),
+					   OCFS2_INODE_UPDATE_CREDITS);
+		if (IS_ERR(handle)) {
+			ret = PTR_ERR(handle);
+			mlog_errno(ret);
+			goto out_brelse;
+		}
+
+		commit_handle = 1;
+	}
+
+	di = (struct ocfs2_dinode *)di_bh->b_data;
+	ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
+				      OCFS2_JOURNAL_ACCESS_WRITE);
+	if (ret) {
+		mlog_errno(ret);
+		goto out_commit;
+	}
+
+	inode->i_mode = new_mode;
+	inode_set_ctime_current(inode);
+	di->i_mode = cpu_to_le16(inode->i_mode);
+	di->i_ctime = cpu_to_le64(inode_get_ctime_sec(inode));
+	di->i_ctime_nsec = cpu_to_le32(inode_get_ctime_nsec(inode));
+	ocfs2_update_inode_fsync_trans(handle, inode, 0);
+
+	ocfs2_journal_dirty(handle, di_bh);
+
+out_commit:
+	if (commit_handle)
+		ocfs2_commit_trans(OCFS2_SB(inode->i_sb), handle);
+out_brelse:
+	brelse(di_bh);
+out:
+	return ret;
+}
+
+/*
+ * Set the access or default ACL of an inode.
+ */
+static int ocfs2_set_acl(handle_t *handle,
+			 struct inode *inode,
+			 struct buffer_head *di_bh,
+			 int type,
+			 struct posix_acl *acl,
+			 struct ocfs2_alloc_context *meta_ac,
+			 struct ocfs2_alloc_context *data_ac)
+{
+	int name_index;
+	void *value = NULL;
+	size_t size = 0;
+	int ret;
+
+	if (S_ISLNK(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		name_index = OCFS2_XATTR_INDEX_POSIX_ACL_ACCESS;
+		break;
+	case ACL_TYPE_DEFAULT:
+		name_index = OCFS2_XATTR_INDEX_POSIX_ACL_DEFAULT;
+		if (!S_ISDIR(inode->i_mode))
+			return acl ? -EACCES : 0;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (acl) {
+		value = ocfs2_acl_to_xattr(acl, &size);
+		if (IS_ERR(value))
+			return (int)PTR_ERR(value);
+	}
+
+	if (handle)
+		ret = ocfs2_xattr_set_handle(handle, inode, di_bh, name_index,
+					     "", value, size, 0,
+					     meta_ac, data_ac);
+	else
+		ret = ocfs2_xattr_set(inode, name_index, "", value, size, 0);
+
+	kfree(value);
+	if (!ret)
+		set_cached_acl(inode, type, acl);
+
+	return ret;
+}
+
+int ocfs2_iop_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
+		      struct posix_acl *acl, int type)
+{
+	struct buffer_head *bh = NULL;
+	int status, had_lock;
+	struct ocfs2_lock_holder oh;
+	struct inode *inode = d_inode(dentry);
+
+	had_lock = ocfs2_inode_lock_tracker(inode, &bh, 1, &oh);
+	if (had_lock < 0)
+		return had_lock;
+	if (type == ACL_TYPE_ACCESS && acl) {
+		umode_t mode;
+
+		status = posix_acl_update_mode(&nop_mnt_idmap, inode, &mode,
+					       &acl);
+		if (status)
+			goto unlock;
+
+		status = ocfs2_acl_set_mode(inode, bh, NULL, mode);
+		if (status)
+			goto unlock;
+	}
+	status = ocfs2_set_acl(NULL, inode, bh, type, acl, NULL, NULL);
+unlock:
+	ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);
+	brelse(bh);
+	return status;
+}
+
+struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type, bool rcu)
+{
+	struct ocfs2_super *osb;
+	struct buffer_head *di_bh = NULL;
+	struct posix_acl *acl;
+	int had_lock;
+	struct ocfs2_lock_holder oh;
+
+	if (rcu)
+		return ERR_PTR(-ECHILD);
+
+	osb = OCFS2_SB(inode->i_sb);
+	if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
+		return NULL;
+
+	had_lock = ocfs2_inode_lock_tracker(inode, &di_bh, 0, &oh);
+	if (had_lock < 0)
+		return ERR_PTR(had_lock);
+
+	down_read(&OCFS2_I(inode)->ip_xattr_sem);
+	acl = ocfs2_get_acl_nolock(inode, type, di_bh);
+	up_read(&OCFS2_I(inode)->ip_xattr_sem);
+
+	ocfs2_inode_unlock_tracker(inode, 0, &oh, had_lock);
+	brelse(di_bh);
+	return acl;
+}
+
+int ocfs2_acl_chmod(struct inode *inode, struct buffer_head *bh)
+{
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+	struct posix_acl *acl;
+	int ret;
+
+	if (S_ISLNK(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
+		return 0;
+
+	down_read(&OCFS2_I(inode)->ip_xattr_sem);
+	acl = ocfs2_get_acl_nolock(inode, ACL_TYPE_ACCESS, bh);
+	up_read(&OCFS2_I(inode)->ip_xattr_sem);
+	if (IS_ERR_OR_NULL(acl))
+		return PTR_ERR_OR_ZERO(acl);
+	ret = __posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
+	if (ret)
+		return ret;
+	ret = ocfs2_set_acl(NULL, inode, NULL, ACL_TYPE_ACCESS,
+			    acl, NULL, NULL);
+	posix_acl_release(acl);
+	return ret;
+}
+
+/*
+ * Initialize the ACLs of a new inode. If parent directory has default ACL,
+ * then clone to new inode. Called from ocfs2_mknod.
+ */
+void ocfs2_acl_init_release(struct ocfs2_acl_state *state)
+{
+	posix_acl_release(state->default_acl);
+	posix_acl_release(state->acl);
+	state->default_acl = NULL;
+	state->acl = NULL;
+}
+
+int ocfs2_acl_init_prepare(struct inode *inode, struct inode *dir,
+			   struct buffer_head *dir_bh,
+			   struct ocfs2_acl_state *state)
+{
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+	int ret = 0;
+
+	state->default_acl = NULL;
+	state->acl = NULL;
+	state->mode = inode->i_mode;
+
+	if (S_ISLNK(inode->i_mode))
+		return 0;
+
+	if (osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) {
+		down_read(&OCFS2_I(dir)->ip_xattr_sem);
+		state->default_acl =
+			ocfs2_get_acl_nolock(dir, ACL_TYPE_DEFAULT, dir_bh);
+		up_read(&OCFS2_I(dir)->ip_xattr_sem);
+		if (IS_ERR(state->default_acl)) {
+			ret = PTR_ERR(state->default_acl);
+			state->default_acl = NULL;
+			return ret;
+		}
+		if (state->default_acl) {
+			state->acl = posix_acl_dup(state->default_acl);
+			if (!state->acl) {
+				ret = -ENOMEM;
+				goto cleanup;
+			}
+			ret = __posix_acl_create(&state->acl, GFP_NOFS,
+						 &state->mode);
+			if (ret < 0)
+				goto cleanup;
+			if (ret == 0) {
+				posix_acl_release(state->acl);
+				state->acl = NULL;
+			}
+			if (!S_ISDIR(inode->i_mode)) {
+				posix_acl_release(state->default_acl);
+				state->default_acl = NULL;
+			}
+		} else {
+			state->mode &= ~current_umask();
+		}
+	} else {
+		state->mode &= ~current_umask();
+	}
+
+	return 0;
+cleanup:
+	ocfs2_acl_init_release(state);
+	return ret;
+}
+
+int ocfs2_init_acl(handle_t *handle, struct inode *inode,
+		   struct buffer_head *di_bh,
+		   struct ocfs2_alloc_context *meta_ac,
+		   struct ocfs2_alloc_context *data_ac,
+		   struct ocfs2_acl_state *state)
+{
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+	int ret = 0;
+
+	if (S_ISLNK(inode->i_mode))
+		return 0;
+
+	if (osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) {
+		if (S_ISDIR(inode->i_mode) && state->default_acl) {
+			ret = ocfs2_set_acl(handle, inode, di_bh,
+					    ACL_TYPE_DEFAULT,
+					    state->default_acl, meta_ac,
+					    data_ac);
+			if (ret)
+				return ret;
+		}
+	}
+
+	ret = ocfs2_acl_set_mode(inode, di_bh, handle, state->mode);
+	if (ret) {
+		mlog_errno(ret);
+		return ret;
+	}
+
+	if (osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) {
+		if (state->acl) {
+			ret = ocfs2_set_acl(handle, inode, di_bh,
+					    ACL_TYPE_ACCESS, state->acl,
+					    meta_ac, data_ac);
+		}
+	}
+
+	return ret;
+}