linux-kernel - [PATCH AUTOSEL 4.19 45/73] ceph: quota: fix null pointer dereference in quota check

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Date:   Wed, 14 Nov 2018 17:21:39 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Luis Henriques <lhenriques@...e.com>,
        Ilya Dryomov <idryomov@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.19 45/73] ceph: quota: fix null pointer dereference in quota check

From: Luis Henriques <lhenriques@...e.com>

[ Upstream commit 71f2cc64d027d712f29bf8d09d3e123302d5f245 ]

This patch fixes a possible null pointer dereference in
check_quota_exceeded, detected by the static checker smatch, with the
following warning:

   fs/ceph/quota.c:240 check_quota_exceeded()
    error: we previously assumed 'realm' could be null (see line 188)

Fixes: b7a2921765cf ("ceph: quota: support for ceph.quota.max_files")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Luis Henriques <lhenriques@...e.com>
Reviewed-by: "Yan, Zheng" <zyan@...hat.com>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ceph/quota.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
index 32d4f13784ba..03f4d24db8fe 100644
--- a/fs/ceph/quota.c
+++ b/fs/ceph/quota.c
@@ -237,7 +237,8 @@ static bool check_quota_exceeded(struct inode *inode, enum quota_check_op op,
 		ceph_put_snap_realm(mdsc, realm);
 		realm = next;
 	}
-	ceph_put_snap_realm(mdsc, realm);
+	if (realm)
+		ceph_put_snap_realm(mdsc, realm);
 	up_read(&mdsc->snap_rwsem);
 
 	return exceeded;
-- 
2.17.1