linux-kernel - [PATCH 5.10 18/29] ceph: fix possible null-pointer dereference in ceph_mdsmap

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Date:   Mon,  6 Sep 2021 14:55:33 +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, TOTE Robot <oslab@...nghua.edu.cn>,
        Tuo Li <islituo@...il.com>, Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 18/29] ceph: fix possible null-pointer dereference in ceph_mdsmap_decode()

From: Tuo Li <islituo@...il.com>

[ Upstream commit a9e6ffbc5b7324b6639ee89028908b1e91ceed51 ]

kcalloc() is called to allocate memory for m->m_info, and if it fails,
ceph_mdsmap_destroy() behind the label out_err will be called:
  ceph_mdsmap_destroy(m);

In ceph_mdsmap_destroy(), m->m_info is dereferenced through:
  kfree(m->m_info[i].export_targets);

To fix this possible null-pointer dereference, check m->m_info before the
for loop to free m->m_info[i].export_targets.

[ jlayton: fix up whitespace damage
	   only kfree(m->m_info) if it's non-NULL ]

Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
Signed-off-by: Tuo Li <islituo@...il.com>
Signed-off-by: Jeff Layton <jlayton@...nel.org>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ceph/mdsmap.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
index 1096d1d3a84c..47f2903bacb9 100644
--- a/fs/ceph/mdsmap.c
+++ b/fs/ceph/mdsmap.c
@@ -393,9 +393,11 @@ void ceph_mdsmap_destroy(struct ceph_mdsmap *m)
 {
 	int i;
 
-	for (i = 0; i < m->possible_max_rank; i++)
-		kfree(m->m_info[i].export_targets);
-	kfree(m->m_info);
+	if (m->m_info) {
+		for (i = 0; i < m->possible_max_rank; i++)
+			kfree(m->m_info[i].export_targets);
+		kfree(m->m_info);
+	}
 	kfree(m->m_data_pg_pools);
 	kfree(m);
 }
-- 
2.30.2