[PATCH] ceph: fix possible null-pointer dereference in ceph_mdsmap_decode()

[Tuo Li]

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, if memory allocation
for m->m_info fails, free m and return -ENOMEM.

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
Signed-off-by: Tuo Li <islituo@xxxxxxxxx>
---
 fs/ceph/mdsmap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c
index abd9af7727ad..7d73e4b64b12 100644
--- a/fs/ceph/mdsmap.c
+++ b/fs/ceph/mdsmap.c
@@ -166,8 +166,10 @@ struct ceph_mdsmap *ceph_mdsmap_decode(void **p, void *end, bool msgr2)
 	m->possible_max_rank = max(m->m_num_active_mds, m->m_max_mds);
 
 	m->m_info = kcalloc(m->possible_max_rank, sizeof(*m->m_info), GFP_NOFS);
-	if (!m->m_info)
-		goto nomem;
+	if (!m->m_info) {
+		kfree(m);
+		return ERR_PTR(-ENOMEM);
+	}
 
 	/* pick out active nodes from mds_info (state > 0) */
 	for (i = 0; i < n; i++) {
-- 
2.25.1