net/packet: fix overflow in check for priv area size

Subtracting tp_sizeof_priv from tp_block_size and casting to int
to check whether one is less then the other doesn't always work
(both of them are unsigned ints).

Compare them as is instead.

Also cast tp_sizeof_priv to u64 before using BLK_PLUS_PRIV, as
it can overflow inside BLK_PLUS_PRIV otherwise.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name net-packet-fix-overflow-in-check-for-priv-area-size.patch

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f2b04a77258d98697ef8b18e860a794c086e686d..8ab0974f4ee2f4a09628872bf3e208bdd7e8d56d 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4235,8 +4235,8 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
                if (unlikely(!PAGE_ALIGNED(req->tp_block_size)))
                        goto out;
                if (po->tp_version >= TPACKET_V3 &&
-                   (int)(req->tp_block_size -
-                         BLK_PLUS_PRIV(req_u->req3.tp_sizeof_priv)) <= 0)
+                   req->tp_block_size <=
+                         BLK_PLUS_PRIV((u64)req_u->req3.tp_sizeof_priv))
                        goto out;
                if (unlikely(req->tp_frame_size < po->tp_hdrlen +
                                        po->tp_reserve))