CVE-2026-74351: ocfs2: rebase copied fsdlm LVB pointers in locking_state

CVE-2026-74351: ocfs2: rebase copied fsdlm LVB pointers in locking_state

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: rebase copied fsdlm LVB pointers in locking_state

The locking_state debugfs iterator snapshots struct ocfs2_lock_res by
value under ocfs2_dlm_tracking_lock and later formats that copy in
ocfs2_dlm_seq_show().  That is fine for the inline fields, but the
userspace fsdlm stack stores the LVB through lksb_fsdlm.sb_lvbptr.  Once
the iterator drops the tracking lock, a copied non-NULL sb_lvbptr still
points into the original lockres owner, so teardown can free that
container before the debugfs dump walks the raw LVB bytes.

Rebase the copied sb_lvbptr to the copied l_lksb before dumping the raw
LVB.  The seq snapshot already carries the inline LVB storage reserved in
struct ocfs2_dlm_lksb, so the debugfs reader can dump the copied bytes
without borrowing the original lockres lifetime.

The buggy scenario involves two paths, with each column showing the order
within that path:

locking_state reader:                  lockres teardown:
1. ocfs2_dlm_seq_start()/next()        1. file release or another owner
   copies struct ocfs2_lock_res           teardown reaches
2. ocfs2_dlm_seq_show() formats           ocfs2_lock_res_free()
   the copied row                      2. the lockres is removed from the
3. ocfs2_dlm_lvb() follows the            tracking list
   copied sb_lvbptr                   3. the owner frees the original
                                          lockres container

Validation reproduced this kernel report:
KASAN slab-use-after-free in ocfs2_dlm_seq_show+0x1bd/0x430
RIP: 0033:0x7f8ec4b1e29d
The buggy address belongs to the object at ffff88810a1e0800 which belongs
to the cache kmalloc-1k of size 1024
The buggy address is located 368 bytes inside of freed 1024-byte region
[ffff88810a1e0800, ffff88810a1e0c00)
Read of size 1
Call trace:
  dump_stack_lvl+0x66/0xa0
  print_report+0xce/0x630
  ocfs2_dlm_seq_show+0x1bd/0x430 (fs/ocfs2/dlmglue.c:3137)
  srso_alias_return_thunk+0x5/0xfbef5
  __virt_addr_valid+0x19f/0x330
  kasan_report+0xe0/0x110
  seq_read_iter+0x29d/0x790
  seq_read+0x20a/0x280
  find_held_lock+0x2b/0x80
  rcu_read_unlock+0x18/0x70
  full_proxy_read+0x9e/0xd0
  vfs_read+0x12c/0x590
  ksys_read+0xd2/0x170
  do_user_addr_fault+0x65a/0x890
  do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
Allocated by task stack:
  kasan_save_stack+0x33/0x60
  kasan_save_track+0x14/0x30
  __kasan_kmalloc+0xaa/0xb0
  ocfs2_file_open+0x13e/0x300
  do_dentry_open+0x233/0x7f0
  vfs_open+0x5a/0x1b0
  path_openat+0x66d/0x1540
  do_file_open+0x186/0x2b0
  do_sys_openat2+0xce/0x150
  __x64_sys_openat+0xd0/0x140
  do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task stack:
  kasan_save_stack+0x33/0x60
  kasan_save_track+0x14/0x30
  kasan_save_free_info+0x3b/0x60
  __kasan_slab_free+0x5f/0x80
  kfree+0x313/0x590
  ocfs2_file_release+0x138/0x260
  __fput+0x1df/0x4b0
  fput_close_sync+0xd2/0x170
  __x64_sys_close+0x55/0x90
  do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)
  entry_SYSCALL_64_after_hwframe+0x77/0x7f

The Linux kernel CVE team has assigned CVE-2026-74351 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 2.6.26 with commit cf4d8d75d8aba537a19b313a9364fd08ddbd5622 and fixed in 5.10.261 with commit 185427b5f7a209254c85c18aad5a4a8e009b2f30
	Issue introduced in 2.6.26 with commit cf4d8d75d8aba537a19b313a9364fd08ddbd5622 and fixed in 5.15.212 with commit 07aa4a8ebacde3d0ba50f60d2964f274ee7629bc
	Issue introduced in 2.6.26 with commit cf4d8d75d8aba537a19b313a9364fd08ddbd5622 and fixed in 6.1.178 with commit e037c1250cc90e7aacb002357d1b0399fc65ecfc
	Issue introduced in 2.6.26 with commit cf4d8d75d8aba537a19b313a9364fd08ddbd5622 and fixed in 6.6.145 with commit 6b38a5b8ee951e5b244e9a3c3d28d0f5e7c51411
	Issue introduced in 2.6.26 with commit cf4d8d75d8aba537a19b313a9364fd08ddbd5622 and fixed in 6.12.97 with commit 8614a8f7e81edd34c9f67e454e7024fd12a2a341
	Issue introduced in 2.6.26 with commit cf4d8d75d8aba537a19b313a9364fd08ddbd5622 and fixed in 6.18.40 with commit bb44a7690a4d553da705919cf666a80f5ca9011c
	Issue introduced in 2.6.26 with commit cf4d8d75d8aba537a19b313a9364fd08ddbd5622 and fixed in 7.1.5 with commit 610a0d2a35496738e1472fb0f318d5008a1c634f
	Issue introduced in 2.6.26 with commit cf4d8d75d8aba537a19b313a9364fd08ddbd5622 and fixed in 7.2-rc1 with commit 93612d48fa42b3d1a637eb9279e15281c611c000

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-74351
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/ocfs2/dlmglue.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/185427b5f7a209254c85c18aad5a4a8e009b2f30
	https://git.kernel.org/stable/c/07aa4a8ebacde3d0ba50f60d2964f274ee7629bc
	https://git.kernel.org/stable/c/e037c1250cc90e7aacb002357d1b0399fc65ecfc
	https://git.kernel.org/stable/c/6b38a5b8ee951e5b244e9a3c3d28d0f5e7c51411
	https://git.kernel.org/stable/c/8614a8f7e81edd34c9f67e454e7024fd12a2a341
	https://git.kernel.org/stable/c/bb44a7690a4d553da705919cf666a80f5ca9011c
	https://git.kernel.org/stable/c/610a0d2a35496738e1472fb0f318d5008a1c634f
	https://git.kernel.org/stable/c/93612d48fa42b3d1a637eb9279e15281c611c000