From dc808110bb62b64a448696ecac3938902c92e1ab Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 15 Aug 2014 09:16:04 -0700 Subject: packet: handle too big packets for PACKET_V3 af_packet can currently overwrite kernel memory by out of bound accesses, because it assumed a [new] block can always hold one frame. This is not generally the case, even if most existing tools do it right. This patch clamps too long frames as API permits, and issue a one time error on syslog. [ 394.357639] tpacket_rcv: packet too big, clamped from 5042 to 3966. macoff=82 In this example, packet header tp_snaplen was set to 3966, and tp_len was set to 5042 (skb->len) Signed-off-by: Eric Dumazet Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.") Acked-by: Daniel Borkmann Acked-by: Neil Horman Signed-off-by: David S. Miller --- net/packet/af_packet.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'net/packet/af_packet.c') diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 8d9f8042705a..93896d2092f6 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -632,6 +632,7 @@ static void init_prb_bdqc(struct packet_sock *po, p1->tov_in_jiffies = msecs_to_jiffies(p1->retire_blk_tov); p1->blk_sizeof_priv = req_u->req3.tp_sizeof_priv; + p1->max_frame_len = p1->kblk_size - BLK_PLUS_PRIV(p1->blk_sizeof_priv); prb_init_ft_ops(p1, req_u); prb_setup_retire_blk_timer(po, tx_ring); prb_open_block(p1, pbd); @@ -1942,6 +1943,18 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, if ((int)snaplen < 0) snaplen = 0; } + } else if (unlikely(macoff + snaplen > + GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len)) { + u32 nval; + + nval = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len - macoff; + pr_err_once("tpacket_rcv: packet too big, clamped from %u to %u. macoff=%u\n", + snaplen, nval, macoff); + snaplen = nval; + if (unlikely((int)snaplen < 0)) { + snaplen = 0; + macoff = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len; + } } spin_lock(&sk->sk_receive_queue.lock); h.raw = packet_current_rx_frame(po, skb, @@ -3783,6 +3796,10 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u, goto out; if (unlikely(req->tp_block_size & (PAGE_SIZE - 1))) goto out; + if (po->tp_version >= TPACKET_V3 && + (int)(req->tp_block_size - + BLK_PLUS_PRIV(req_u->req3.tp_sizeof_priv)) <= 0) + goto out; if (unlikely(req->tp_frame_size < po->tp_hdrlen + po->tp_reserve)) goto out; -- cgit v1.2.3