af_packet: avoid a false positive warning in packet_setsockopt()

[ Upstream commit 86d43e2 ] Although the code is correct, the following line copy_from_sockptr(&req_u.req, optval, len)); triggers this warning : memcpy: detected field-spanning write (size 28) of single field "dst" at include/linux/sockptr.h:49 (size 16) Refactor the code to be more explicit. Reported-by: syzbot <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Cc: Kees Cook <[email protected]> Cc: Willem de Bruijn <[email protected]> Reviewed-by: Kees Cook <[email protected]> Reviewed-by: Willem de Bruijn <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
ruyisdk · Jun 27, 2024 · c572d3a · c572d3a
1 parent 946a635
commit c572d3a
Showing 1 changed file with 14 additions and 12 deletions.
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
@@ -3805,28 +3805,30 @@ packet_setsockopt(struct socket *sock, int level, int optname, sockptr_t optval,
 	case PACKET_TX_RING:
 	{
 		union tpacket_req_u req_u;
-		int len;
 
+		ret = -EINVAL;
 		lock_sock(sk);
 		switch (po->tp_version) {
 		case TPACKET_V1:
 		case TPACKET_V2:
-			len = sizeof(req_u.req);
+			if (optlen < sizeof(req_u.req))
+				break;
+			ret = copy_from_sockptr(&req_u.req, optval,
+						sizeof(req_u.req)) ?
+						-EINVAL : 0;
 			break;
 		case TPACKET_V3:
 		default:
-			len = sizeof(req_u.req3);
+			if (optlen < sizeof(req_u.req3))
+				break;
+			ret = copy_from_sockptr(&req_u.req3, optval,
+						sizeof(req_u.req3)) ?
+						-EINVAL : 0;
 			break;
 		}
-		if (optlen < len) {
-			ret = -EINVAL;
-		} else {
-			if (copy_from_sockptr(&req_u.req, optval, len))
-				ret = -EFAULT;
-			else
-				ret = packet_set_ring(sk, &req_u, 0,
-						    optname == PACKET_TX_RING);
-		}
+		if (!ret)
+			ret = packet_set_ring(sk, &req_u, 0,
+					      optname == PACKET_TX_RING);
 		release_sock(sk);
 		return ret;
 	}