libceph: fix overflow in osdmap_apply_incremental()

On 32-bit systems, a large `pglen' would overflow `pglen*sizeof(u32)'
and bypass the check ceph_decode_need(p, end, pglen*sizeof(u32), bad).
It would also overflow the subsequent kmalloc() size, leading to
out-of-bounds write.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Reviewed-by: Alex Elder <elder@inktank.com>

diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
index d70aaca..d3de09f 100644 (file)
--- a/net/ceph/osdmap.c
+++ b/net/ceph/osdmap.c
@@ -893,6 +893,10 @@ struct ceph_osdmap *osdmap_apply_incremental(void **p, void *end,
                        (void) __remove_pg_mapping(&map->pg_temp, pgid);
 
                        /* insert */
+                       if (pglen > (UINT_MAX - sizeof(*pg)) / sizeof(u32)) {
+                               err = -EINVAL;
+                               goto bad;
+                       }
                        pg = kmalloc(sizeof(*pg) + sizeof(u32)*pglen, GFP_NOFS);
                        if (!pg) {
                                err = -ENOMEM;