diff options
| author | Eric Dumazet <edumazet@google.com> | 2017-04-26 17:15:40 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-04-28 16:05:22 -0400 |
| commit | 7162fb242cb8322beb558828fd26b33c3e9fc805 (patch) | |
| tree | 1d4240e28de77ffaf2180f17f3314b26a7bd1258 /net | |
| parent | 19cdead3e2ef8ed765c5d1ce48057ca9d97b5094 (diff) | |
tcp: do not underestimate skb->truesize in tcp_trim_head()
Andrey found a way to trigger the WARN_ON_ONCE(delta < len) in
skb_try_coalesce() using syzkaller and a filter attached to a TCP
socket over loopback interface.
I believe one issue with looped skbs is that tcp_trim_head() can end up
producing skb with under estimated truesize.
It hardly matters for normal conditions, since packets sent over
loopback are never truncated.
Bytes trimmed from skb->head should not change skb truesize, since
skb->head is not reallocated.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/tcp_output.c | 19 |
1 files changed, 12 insertions, 7 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index c3c082ed3879..a85d863c4419 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1267,7 +1267,7 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, * eventually). The difference is that pulled data not copied, but * immediately discarded. */ -static void __pskb_trim_head(struct sk_buff *skb, int len) +static int __pskb_trim_head(struct sk_buff *skb, int len) { struct skb_shared_info *shinfo; int i, k, eat; @@ -1277,7 +1277,7 @@ static void __pskb_trim_head(struct sk_buff *skb, int len) __skb_pull(skb, eat); len -= eat; if (!len) - return; + return 0; } eat = len; k = 0; @@ -1303,23 +1303,28 @@ static void __pskb_trim_head(struct sk_buff *skb, int len) skb_reset_tail_pointer(skb); skb->data_len -= len; skb->len = skb->data_len; + return len; } /* Remove acked data from a packet in the transmit queue. */ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) { + u32 delta_truesize; + if (skb_unclone(skb, GFP_ATOMIC)) return -ENOMEM; - __pskb_trim_head(skb, len); + delta_truesize = __pskb_trim_head(skb, len); TCP_SKB_CB(skb)->seq += len; skb->ip_summed = CHECKSUM_PARTIAL; - skb->truesize -= len; - sk->sk_wmem_queued -= len; - sk_mem_uncharge(sk, len); - sock_set_flag(sk, SOCK_QUEUE_SHRUNK); + if (delta_truesize) { + skb->truesize -= delta_truesize; + sk->sk_wmem_queued -= delta_truesize; + sk_mem_uncharge(sk, delta_truesize); + sock_set_flag(sk, SOCK_QUEUE_SHRUNK); + } /* Any change of skb->len requires recalculation of tso factor. */ if (tcp_skb_pcount(skb) > 1) |