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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-10-17 17:59:53 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2011-10-19 03:50:43 -0400 |
| commit | 4ea2739ea89883ddf79980a8aa27d5e57093e464 (patch) | |
| tree | 4ce1a9760251a507839c0e645dae109c036ec727 /drivers | |
| parent | 58af19e387d8821927e49be3f467da5e6a0aa8fd (diff) | |
| download | lwn-4ea2739ea89883ddf79980a8aa27d5e57093e464.tar.gz lwn-4ea2739ea89883ddf79980a8aa27d5e57093e464.zip | |
pptp: pptp_rcv_core() misses pskb_may_pull() call
e1000e uses paged frags, so any layer incorrectly pulling bytes from skb
can trigger a BUG in skb_pull()
[951.142737] [<ffffffff813d2f36>] skb_pull+0x15/0x17
[951.142737] [<ffffffffa0286824>] pptp_rcv_core+0x126/0x19a [pptp]
[951.152725] [<ffffffff813d17c4>] sk_receive_skb+0x69/0x105
[951.163558] [<ffffffffa0286993>] pptp_rcv+0xc8/0xdc [pptp]
[951.165092] [<ffffffffa02800a3>] gre_rcv+0x62/0x75 [gre]
[951.165092] [<ffffffff81410784>] ip_local_deliver_finish+0x150/0x1c1
[951.177599] [<ffffffff81410634>] ? ip_local_deliver_finish+0x0/0x1c1
[951.177599] [<ffffffff81410846>] NF_HOOK.clone.7+0x51/0x58
[951.177599] [<ffffffff81410996>] ip_local_deliver+0x51/0x55
[951.177599] [<ffffffff814105b9>] ip_rcv_finish+0x31a/0x33e
[951.177599] [<ffffffff8141029f>] ? ip_rcv_finish+0x0/0x33e
[951.204898] [<ffffffff81410846>] NF_HOOK.clone.7+0x51/0x58
[951.214651] [<ffffffff81410bb5>] ip_rcv+0x21b/0x246
pptp_rcv_core() is a nice example of a function assuming everything it
needs is available in skb head.
Reported-by: Bradley Peterson <despite@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/pptp.c | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/drivers/net/pptp.c b/drivers/net/pptp.c index 9c0403d0107c..89f829f5f725 100644 --- a/drivers/net/pptp.c +++ b/drivers/net/pptp.c @@ -307,11 +307,18 @@ static int pptp_rcv_core(struct sock *sk, struct sk_buff *skb) } header = (struct pptp_gre_header *)(skb->data); + headersize = sizeof(*header); /* test if acknowledgement present */ if (PPTP_GRE_IS_A(header->ver)) { - __u32 ack = (PPTP_GRE_IS_S(header->flags)) ? - header->ack : header->seq; /* ack in different place if S = 0 */ + __u32 ack; + + if (!pskb_may_pull(skb, headersize)) + goto drop; + header = (struct pptp_gre_header *)(skb->data); + + /* ack in different place if S = 0 */ + ack = PPTP_GRE_IS_S(header->flags) ? header->ack : header->seq; ack = ntohl(ack); @@ -320,21 +327,18 @@ static int pptp_rcv_core(struct sock *sk, struct sk_buff *skb) /* also handle sequence number wrap-around */ if (WRAPPED(ack, opt->ack_recv)) opt->ack_recv = ack; + } else { + headersize -= sizeof(header->ack); } - /* test if payload present */ if (!PPTP_GRE_IS_S(header->flags)) goto drop; - headersize = sizeof(*header); payload_len = ntohs(header->payload_len); seq = ntohl(header->seq); - /* no ack present? */ - if (!PPTP_GRE_IS_A(header->ver)) - headersize -= sizeof(header->ack); /* check for incomplete packet (length smaller than expected) */ - if (skb->len - headersize < payload_len) + if (!pskb_may_pull(skb, headersize + payload_len)) goto drop; payload = skb->data + headersize; |