[PATCH] lockd: fix NULL dereference on lockowner allocation failure

[Shuangpeng Bai]

nlmclnt_locks_init_private() installs NLM file lock operations even when
nlmclnt_find_lockowner() fails to allocate a lockowner. nlmclnt_proc()
then returns -ENOMEM, but the VFS still tears down the partially
initialized file_lock and calls locks_release_private().

That invokes nlmclnt_locks_release_private(), which dereferences
fl->fl_u.nfs_fl.owner and crashes because the owner was never installed.

Clear fl_ops before attempting to initialize the NLM private state, and
install the NLM lock operations only after a lockowner has been allocated
successfully.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Shuangpeng Bai <shuangpeng.kernel@xxxxxxxxx>
---
 fs/lockd/clntproc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index f06faf577cea..f8018bfe9c64 100644
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -487,9 +487,12 @@ static const struct file_lock_operations nlmclnt_lock_ops = {
 static void nlmclnt_locks_init_private(struct file_lock *fl, struct nlm_host *host)
 {
 	fl->fl_u.nfs_fl.state = 0;
+	fl->fl_ops = NULL;
 	fl->fl_u.nfs_fl.owner = nlmclnt_find_lockowner(host,
 						       fl->c.flc_owner);
 	INIT_LIST_HEAD(&fl->fl_u.nfs_fl.list);
+	if (!fl->fl_u.nfs_fl.owner)
+		return;
 	fl->fl_ops = &nlmclnt_lock_ops;
 }
 

base-commit: fce2dfa773ced15f27dd27cd0b482a7473cdcf2a
-- 
2.43.0