ksmbd: call ksmbd_vfs_kern_path_end_removing() on some error paths

[PATCH] ksmbd: call ksmbd_vfs_kern_path_end_removing() on some error paths

Posted by Fedor Pchelkin 1 month, 2 weeks ago

There are two places where ksmbd_vfs_kern_path_end_removing() needs to be
called in order to balance what the corresponding successful call to
ksmbd_vfs_kern_path_start_removing() has done, i.e. drop inode locks and
put the taken references.  Otherwise there might be potential deadlocks
and unbalanced locks which are caught like:

BUG: workqueue leaked lock or atomic: kworker/5:21/0x00000000/7596
     last function: handle_ksmbd_work
2 locks held by kworker/5:21/7596:
 #0: ffff8881051ae448 (sb_writers#3){.+.+}-{0:0}, at: ksmbd_vfs_kern_path_locked+0x142/0x660
 #1: ffff888130e966c0 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: ksmbd_vfs_kern_path_locked+0x17d/0x660
CPU: 5 PID: 7596 Comm: kworker/5:21 Not tainted 6.1.162-00456-gc29b353f383b #138
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
Workqueue: ksmbd-io handle_ksmbd_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x44/0x5b
 process_one_work.cold+0x57/0x5c
 worker_thread+0x82/0x600
 kthread+0x153/0x190
 ret_from_fork+0x22/0x30
 </TASK>

Found by Linux Verification Center (linuxtesting.org).

Fixes: d5fc1400a34b ("smb/server: avoid deadlock when linking with ReplaceIfExists")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
---
 fs/smb/server/smb2pdu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index cbb31efdbaa2..2782eea214d0 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -6115,14 +6115,14 @@ static int smb2_create_link(struct ksmbd_work *work,
 				rc = -EINVAL;
 				ksmbd_debug(SMB, "cannot delete %s\n",
 					    link_name);
-				goto out;
 			}
 		} else {
 			rc = -EEXIST;
 			ksmbd_debug(SMB, "link already exists\n");
-			goto out;
 		}
 		ksmbd_vfs_kern_path_end_removing(&path);
+		if (rc)
+			goto out;
 	}
 	rc = ksmbd_vfs_link(work, target_name, link_name);
 	if (rc)
-- 
2.51.0

Re: [PATCH] ksmbd: call ksmbd_vfs_kern_path_end_removing() on some error paths

Posted by Namjae Jeon 1 month, 2 weeks ago

On Sun, Feb 15, 2026 at 12:45 AM Fedor Pchelkin <pchelkin@ispras.ru> wrote:
>
> There are two places where ksmbd_vfs_kern_path_end_removing() needs to be
> called in order to balance what the corresponding successful call to
> ksmbd_vfs_kern_path_start_removing() has done, i.e. drop inode locks and
> put the taken references.  Otherwise there might be potential deadlocks
> and unbalanced locks which are caught like:
>
> BUG: workqueue leaked lock or atomic: kworker/5:21/0x00000000/7596
>      last function: handle_ksmbd_work
> 2 locks held by kworker/5:21/7596:
>  #0: ffff8881051ae448 (sb_writers#3){.+.+}-{0:0}, at: ksmbd_vfs_kern_path_locked+0x142/0x660
>  #1: ffff888130e966c0 (&type->i_mutex_dir_key#3/1){+.+.}-{4:4}, at: ksmbd_vfs_kern_path_locked+0x17d/0x660
> CPU: 5 PID: 7596 Comm: kworker/5:21 Not tainted 6.1.162-00456-gc29b353f383b #138
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
> Workqueue: ksmbd-io handle_ksmbd_work
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x44/0x5b
>  process_one_work.cold+0x57/0x5c
>  worker_thread+0x82/0x600
>  kthread+0x153/0x190
>  ret_from_fork+0x22/0x30
>  </TASK>
>
> Found by Linux Verification Center (linuxtesting.org).
>
> Fixes: d5fc1400a34b ("smb/server: avoid deadlock when linking with ReplaceIfExists")
> Cc: stable@vger.kernel.org
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Applied it to #ksmbd-for-next-next.
Thanks!