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authorEric Dumazet <edumazet@google.com>2014-08-15 09:16:04 -0700
committerDavid S. Miller <davem@davemloft.net>2014-08-21 16:44:28 -0700
commitdc808110bb62b64a448696ecac3938902c92e1ab (patch)
tree05abe4d611d696d3b64c24c9cfac048b6d9db0f0
parent564ee3606fe6c9e014c4bee9d74a5eaef96034c8 (diff)
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 <edumazet@google.com> Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.") Acked-by: Daniel Borkmann <dborkman@redhat.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/packet/af_packet.c17
-rw-r--r--net/packet/internal.h1
2 files changed, 18 insertions, 0 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 8d9f8042705..93896d2092f 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;
diff --git a/net/packet/internal.h b/net/packet/internal.h
index eb9580a6b25..cdddf6a3039 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -29,6 +29,7 @@ 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;