Re: [PATCH 6.1.y] smb: prevent use-after-free due to open_cached_dir error paths

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Hi,

There is upstream id in my local patch, but it is discarded by 'git shend-mail'.

Please ignore this patch. I'll check the reason and send it later.

So sorry for my mistake.

Thanks,

  Cliff

On 2025/3/19 22:03, Greg KH wrote:
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On Wed, Mar 19, 2025 at 05:08:39PM +0800, Cliff Liu wrote:
From: Paul Aurich <paul@xxxxxxxxxxxxxx>

If open_cached_dir() encounters an error parsing the lease from the
server, the error handling may race with receiving a lease break,
resulting in open_cached_dir() freeing the cfid while the queued work is
pending.

Update open_cached_dir() to drop refs rather than directly freeing the
cfid.

Have cached_dir_lease_break(), cfids_laundromat_worker(), and
invalidate_all_cached_dirs() clear has_lease immediately while still
holding cfids->cfid_list_lock, and then use this to also simplify the
reference counting in cfids_laundromat_worker() and
invalidate_all_cached_dirs().

Fixes this KASAN splat (which manually injects an error and lease break
in open_cached_dir()):

==================================================================
BUG: KASAN: slab-use-after-free in smb2_cached_lease_break+0x27/0xb0
Read of size 8 at addr ffff88811cc24c10 by task kworker/3:1/65

CPU: 3 UID: 0 PID: 65 Comm: kworker/3:1 Not tainted 6.12.0-rc6-g255cf264e6e5-dirty #87
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020
Workqueue: cifsiod smb2_cached_lease_break
Call Trace:
  <TASK>
  dump_stack_lvl+0x77/0xb0
  print_report+0xce/0x660
  kasan_report+0xd3/0x110
  smb2_cached_lease_break+0x27/0xb0
  process_one_work+0x50a/0xc50
  worker_thread+0x2ba/0x530
  kthread+0x17c/0x1c0
  ret_from_fork+0x34/0x60
  ret_from_fork_asm+0x1a/0x30
  </TASK>

Allocated by task 2464:
  kasan_save_stack+0x33/0x60
  kasan_save_track+0x14/0x30
  __kasan_kmalloc+0xaa/0xb0
  open_cached_dir+0xa7d/0x1fb0
  smb2_query_path_info+0x43c/0x6e0
  cifs_get_fattr+0x346/0xf10
  cifs_get_inode_info+0x157/0x210
  cifs_revalidate_dentry_attr+0x2d1/0x460
  cifs_getattr+0x173/0x470
  vfs_statx_path+0x10f/0x160
  vfs_statx+0xe9/0x150
  vfs_fstatat+0x5e/0xc0
  __do_sys_newfstatat+0x91/0xf0
  do_syscall_64+0x95/0x1a0
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 2464:
  kasan_save_stack+0x33/0x60
  kasan_save_track+0x14/0x30
  kasan_save_free_info+0x3b/0x60
  __kasan_slab_free+0x51/0x70
  kfree+0x174/0x520
  open_cached_dir+0x97f/0x1fb0
  smb2_query_path_info+0x43c/0x6e0
  cifs_get_fattr+0x346/0xf10
  cifs_get_inode_info+0x157/0x210
  cifs_revalidate_dentry_attr+0x2d1/0x460
  cifs_getattr+0x173/0x470
  vfs_statx_path+0x10f/0x160
  vfs_statx+0xe9/0x150
  vfs_fstatat+0x5e/0xc0
  __do_sys_newfstatat+0x91/0xf0
  do_syscall_64+0x95/0x1a0
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

Last potentially related work creation:
  kasan_save_stack+0x33/0x60
  __kasan_record_aux_stack+0xad/0xc0
  insert_work+0x32/0x100
  __queue_work+0x5c9/0x870
  queue_work_on+0x82/0x90
  open_cached_dir+0x1369/0x1fb0
  smb2_query_path_info+0x43c/0x6e0
  cifs_get_fattr+0x346/0xf10
  cifs_get_inode_info+0x157/0x210
  cifs_revalidate_dentry_attr+0x2d1/0x460
  cifs_getattr+0x173/0x470
  vfs_statx_path+0x10f/0x160
  vfs_statx+0xe9/0x150
  vfs_fstatat+0x5e/0xc0
  __do_sys_newfstatat+0x91/0xf0
  do_syscall_64+0x95/0x1a0
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

The buggy address belongs to the object at ffff88811cc24c00
  which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 16 bytes inside of
  freed 1024-byte region [ffff88811cc24c00, ffff88811cc25000)

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Paul Aurich <paul@xxxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
[ Do not apply the change for cfids_laundromat_worker() since there is no
   this function and related feature on 6.1.y. Update open_cached_dir()
   according to method of upstream patch. ]
Signed-off-by: Cliff Liu <donghua.liu@xxxxxxxxxxxxx>
Signed-off-by: He Zhe <Zhe.He@xxxxxxxxxxxxx>
---
Verified the build test.
---
  fs/smb/client/cached_dir.c | 39 ++++++++++++++++----------------------
  1 file changed, 16 insertions(+), 23 deletions(-)
No upstream git id :(




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