[PATCH 5.15.y] smb: client: fix use-after-free bug in cifs_debug_data_proc_show()

[PATCH 5.15.y] smb: client: fix use-after-free bug in cifs_debug_data_proc_show()

[Xiangyu Chen]

From: Paulo Alcantara <pc@manguebit.com>

commit d328c09ee9f15ee5a26431f5aad7c9239fa85e62 upstream.

Skip SMB sessions that are being teared down
(e.g. @ses->ses_status == SES_EXITING) in cifs_debug_data_proc_show()
to avoid use-after-free in @ses.

This fixes the following GPF when reading from /proc/fs/cifs/DebugData
while mounting and umounting

  [ 816.251274] general protection fault, probably for non-canonical
  address 0x6b6b6b6b6b6b6d81: 0000 [#1] PREEMPT SMP NOPTI
  ...
  [  816.260138] Call Trace:
  [  816.260329]  <TASK>
  [  816.260499]  ? die_addr+0x36/0x90
  [  816.260762]  ? exc_general_protection+0x1b3/0x410
  [  816.261126]  ? asm_exc_general_protection+0x26/0x30
  [  816.261502]  ? cifs_debug_tcon+0xbd/0x240 [cifs]
  [  816.261878]  ? cifs_debug_tcon+0xab/0x240 [cifs]
  [  816.262249]  cifs_debug_data_proc_show+0x516/0xdb0 [cifs]
  [  816.262689]  ? seq_read_iter+0x379/0x470
  [  816.262995]  seq_read_iter+0x118/0x470
  [  816.263291]  proc_reg_read_iter+0x53/0x90
  [  816.263596]  ? srso_alias_return_thunk+0x5/0x7f
  [  816.263945]  vfs_read+0x201/0x350
  [  816.264211]  ksys_read+0x75/0x100
  [  816.264472]  do_syscall_64+0x3f/0x90
  [  816.264750]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
  [  816.265135] RIP: 0033:0x7fd5e669d381

Cc: stable@vger.kernel.org
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
[ This patch removed lock/unlock operation due to ses_lock is
not present in v5.15 and not ported yet. ses->status is protected
by a global lock, cifs_tcp_ses_lock, in v5.15. ]
Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com>
Signed-off-by: He Zhe <zhe.he@windriver.com>
---
Verified build test.
---
 fs/cifs/cifs_debug.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index e7501533c2ec..c90f51c12fb0 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -380,6 +380,8 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 		list_for_each(tmp2, &server->smb_ses_list) {
 			ses = list_entry(tmp2, struct cifs_ses,
 					 smb_ses_list);
+			if (ses->status == CifsExiting)
+				continue;
 			i++;
 			if ((ses->serverDomain == NULL) ||
 				(ses->serverOS == NULL) ||
-- 
2.43.0

Re: [PATCH 5.15.y] smb: client: fix use-after-free bug in cifs_debug_data_proc_show()

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: d328c09ee9f15ee5a26431f5aad7c9239fa85e62

WARNING: Author mismatch between patch and upstream commit:
Backport author: Xiangyu Chen<xiangyu.chen@eng.windriver.com>
Commit author: Paulo Alcantara<pc@manguebit.com>

Status in newer kernel trees:
6.13.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (different SHA1: 0ab6f842452c)
6.1.y | Present (different SHA1: 558817597d5f)

Note: The patch differs from the upstream commit:
---
1:  d328c09ee9f15 < -:  ------------- smb: client: fix use-after-free bug in cifs_debug_data_proc_show()
-:  ------------- > 1:  eb18335a35941 smb: client: fix use-after-free bug in cifs_debug_data_proc_show()
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |