From 9f2e63f1b2d5fc5b5423424902c091123e220e7e Mon Sep 17 00:00:00 2001 From: Bjoern Doebel Date: Thu, 3 Sep 2026 21:28:58 +0000 Subject: [PATCH] smb: client: avoid leaking refcount in cifs_queue_oplock_break() cifs_queue_oplock_break() unconditionally takes a reference on the target file before queueing cifs_oplock_break(). Only that work item decreases the reference counter again. If another oplock break arrives while that work is still queued, queue_work() will return false and not queue this second work item. As a result, we will never reach the point to drop the file reference again and are leaking this reference. This can be triggered when interacting with a slow-responding server. As a result, later unmount operations for this file system will fail with BUG: Dentry ... still in use (1) [unmount of cifs cifs] VFS: Busy inodes after unmount of cifs (cifs) kernel BUG at fs/super.c:777! Fix this by only incrementing the reference count if the work has been queued successfully. Taking it after queue_work() is safe because all three callers hold tcon->open_file_lock across the call and _cifsFileInfo_put() decrements under that same lock, so a worker that starts the handler in the window cannot drop the reference before it has been taken. Fixes: b98749cac4a69 ("CIFS: keep FileInfo handle live during oplock break") Cc: stable@vger.kernel.org Assisted-by: Kiro:claude-opus-5 Signed-off-by: Bjoern Doebel Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara --- fs/smb/client/misc.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c index d4db3f91a91f..945194fe7a97 100644 --- a/fs/smb/client/misc.c +++ b/fs/smb/client/misc.c @@ -378,10 +378,11 @@ void cifs_queue_oplock_break(struct cifsFileInfo *cfile) * open_file_lock to enforce the validity of it for the oplock * break handler. The matching put is done at the end of the * handler. + * + * Only take a reference if the work is actually queued. */ - cifsFileInfo_get(cfile); - - queue_work(cifsoplockd_wq, &cfile->oplock_break); + if (queue_work(cifsoplockd_wq, &cfile->oplock_break)) + cifsFileInfo_get(cfile); } void cifs_done_oplock_break(struct cifsInodeInfo *cinode)