3.2.89-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Eric Dumazet <[email protected]> commit dc808110bb62b64a448696ecac3938902c92e1ab upstream. 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 <[email protected]> Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.") Acked-by: Daniel Borkmann <[email protected]> Acked-by: Neil Horman <[email protected]> Signed-off-by: David S. Miller <[email protected]> [bwh: Backported to 3.2: adjust filename] Signed-off-by: Ben Hutchings <[email protected]> --- --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -195,6 +195,7 @@ struct tpacket_kbdq_core { char *pkblk_start; char *pkblk_end; int kblk_size; + unsigned int max_frame_len; unsigned int knum_blocks; uint64_t knxt_seq_num; char *prev; @@ -616,6 +617,7 @@ static void init_prb_bdqc(struct packet_ 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); @@ -1775,6 +1777,18 @@ static int tpacket_rcv(struct sk_buff *s 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, @@ -3622,6 +3636,10 @@ static int packet_set_ring(struct sock * 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;
