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ksmbd: fix memory leaks and NULL deref in smb2_lock()

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smb2_lock() has three error handling issues after list_del() detaches
smb_lock from lock_list at no_check_cl:

1) If vfs_lock_file() returns an unexpected error in the non-UNLOCK
   path, goto out leaks smb_lock and its flock because the out:
   handler only iterates lock_list and rollback_list, neither of
   which contains the detached smb_lock.

2) If vfs_lock_file() returns -ENOENT in the UNLOCK path, goto out
   leaks smb_lock and flock for the same reason.  The error code
   returned to the dispatcher is also stale.

3) In the rollback path, smb_flock_init() can return NULL on
   allocation failure.  The result is dereferenced unconditionally,
   causing a kernel NULL pointer dereference.  Add a NULL check to
   prevent the crash and clean up the bookkeeping; the VFS lock
   itself cannot be rolled back without the allocation and will be
   released at file or connection teardown.

Fix cases 1 and 2 by hoisting the locks_free_lock()/kfree() to before
the if(!rc) check in the UNLOCK branch so all exit paths share one
free site, and by freeing smb_lock and flock before goto out in the
non-UNLOCK branch.  Propagate the correct error code in both cases.
Fix case 3 by wrapping the VFS unlock in an if(rlock) guard and adding
a NULL check for locks_free_lock(rlock) in the shared cleanup.

Found via call-graph analysis using sqry.

Fixes: e2f34481b2 ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Suggested-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Signed-off-by: Werner Kasselman <werner@verivus.com>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Werner Kasselman 2026-03-17 07:55:37 +00:00 committed by Steve French
parent 48623ec358
commit 309b44ed68
1 changed files with 18 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
fs/smb/server/smb2pdu.c
View File

@ -7592,14 +7592,15 @@ int smb2_lock(struct ksmbd_work *work)
rc = vfs_lock_file(filp, smb_lock->cmd, flock, NULL);
skip:
if (smb_lock->flags & SMB2_LOCKFLAG_UNLOCK) {
locks_free_lock(flock);
kfree(smb_lock);
if (!rc) {
ksmbd_debug(SMB, "File unlocked\n");
} else if (rc == -ENOENT) {
rsp->hdr.Status = STATUS_NOT_LOCKED;
err = rc;
goto out;
}
locks_free_lock(flock);
kfree(smb_lock);
} else {
if (rc == FILE_LOCK_DEFERRED) {
void **argv;
@ -7668,6 +7669,9 @@ int smb2_lock(struct ksmbd_work *work)
spin_unlock(&work->conn->llist_lock);
ksmbd_debug(SMB, "successful in taking lock\n");
} else {
locks_free_lock(flock);
kfree(smb_lock);
err = rc;
goto out;
}
}
@ -7698,13 +7702,17 @@ int smb2_lock(struct ksmbd_work *work)
struct file_lock *rlock = NULL;
rlock = smb_flock_init(filp);
rlock->c.flc_type = F_UNLCK;
rlock->fl_start = smb_lock->start;
rlock->fl_end = smb_lock->end;
if (rlock) {
rlock->c.flc_type = F_UNLCK;
rlock->fl_start = smb_lock->start;
rlock->fl_end = smb_lock->end;
rc = vfs_lock_file(filp, F_SETLK, rlock, NULL);
if (rc)
pr_err("rollback unlock fail : %d\n", rc);
rc = vfs_lock_file(filp, F_SETLK, rlock, NULL);
if (rc)
pr_err("rollback unlock fail : %d\n", rc);
} else {
pr_err("rollback unlock alloc failed\n");
}
list_del(&smb_lock->llist);
spin_lock(&work->conn->llist_lock);
@ -7714,7 +7722,8 @@ int smb2_lock(struct ksmbd_work *work)
spin_unlock(&work->conn->llist_lock);
locks_free_lock(smb_lock->fl);
locks_free_lock(rlock);
if (rlock)
locks_free_lock(rlock);
kfree(smb_lock);
}
out2: