libceph: fix overflow in osdmap_decode()

On 32-bit systems, a large `n' would overflow `n * sizeof(u32)' and bypass the check ceph_decode_need(p, end, n * sizeof(u32), bad). It would also overflow the subsequent kmalloc() size, leading to out-of-bounds write. Signed-off-by: Xi Wang <[email protected]> Reviewed-by: Alex Elder <[email protected]>
akeromi · Jun 7, 2012 · e91a9b6 · e91a9b6
1 parent ad3b904
commit e91a9b6
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
@@ -667,6 +667,9 @@ struct ceph_osdmap *osdmap_decode(void **p, void *end)
 		ceph_decode_need(p, end, sizeof(u32) + sizeof(u64), bad);
 		ceph_decode_copy(p, &pgid, sizeof(pgid));
 		n = ceph_decode_32(p);
+		err = -EINVAL;
+		if (n > (UINT_MAX - sizeof(*pg)) / sizeof(u32))
+			goto bad;
 		ceph_decode_need(p, end, n * sizeof(u32), bad);
 		err = -ENOMEM;
 		pg = kmalloc(sizeof(*pg) + n*sizeof(u32), GFP_NOFS);