linux-kernel - [PATCH 5.10 165/236] lockd: Fix invalid lockowner cast after vfs_test

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Message-Id: <20210913131105.991491498@linuxfoundation.org>
Date:   Mon, 13 Sep 2021 15:14:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Benjamin Coddington <bcodding@...hat.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 165/236] lockd: Fix invalid lockowner cast after vfs_test_lock

From: Benjamin Coddington <bcodding@...hat.com>

[ Upstream commit cd2d644ddba183ec7b451b7c20d5c7cc06fcf0d7 ]

After calling vfs_test_lock() the pointer to a conflicting lock can be
returned, and that lock is not guarunteed to be owned by nlm.  In that
case, we cannot cast it to struct nlm_lockowner.  Instead return the pid
of that conflicting lock.

Fixes: 646d73e91b42 ("lockd: Show pid of lockd for remote locks")
Signed-off-by: Benjamin Coddington <bcodding@...hat.com>
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/lockd/svclock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index 61d3cc2283dc..498cb70c2c0d 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -634,7 +634,7 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
 	conflock->caller = "somehost";	/* FIXME */
 	conflock->len = strlen(conflock->caller);
 	conflock->oh.len = 0;		/* don't return OH info */
-	conflock->svid = ((struct nlm_lockowner *)lock->fl.fl_owner)->pid;
+	conflock->svid = lock->fl.fl_pid;
 	conflock->fl.fl_type = lock->fl.fl_type;
 	conflock->fl.fl_start = lock->fl.fl_start;
 	conflock->fl.fl_end = lock->fl.fl_end;
-- 
2.30.2