| From foo@baz Wed Apr 29 11:59:49 CEST 2015 |
| From: Eric Dumazet <edumazet@google.com> |
| Date: Tue, 21 Apr 2015 18:32:24 -0700 |
| Subject: tcp: fix possible deadlock in tcp_send_fin() |
| |
| From: Eric Dumazet <edumazet@google.com> |
| |
| [ Upstream commit d83769a580f1132ac26439f50068a29b02be535e ] |
| |
| Using sk_stream_alloc_skb() in tcp_send_fin() is dangerous in |
| case a huge process is killed by OOM, and tcp_mem[2] is hit. |
| |
| To be able to free memory we need to make progress, so this |
| patch allows FIN packets to not care about tcp_mem[2], if |
| skb allocation succeeded. |
| |
| In a follow-up patch, we might abort tcp_send_fin() infinite loop |
| in case TIF_MEMDIE is set on this thread, as memory allocator |
| did its best getting extra memory already. |
| |
| This patch reverts d22e15371811 ("tcp: fix tcp fin memory accounting") |
| |
| Fixes: d22e15371811 ("tcp: fix tcp fin memory accounting") |
| Signed-off-by: Eric Dumazet <edumazet@google.com> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| net/ipv4/tcp_output.c | 20 +++++++++++++++++++- |
| 1 file changed, 19 insertions(+), 1 deletion(-) |
| |
| --- a/net/ipv4/tcp_output.c |
| +++ b/net/ipv4/tcp_output.c |
| @@ -2751,6 +2751,21 @@ begin_fwd: |
| } |
| } |
| |
| +/* We allow to exceed memory limits for FIN packets to expedite |
| + * connection tear down and (memory) recovery. |
| + * Otherwise tcp_send_fin() could loop forever. |
| + */ |
| +static void sk_forced_wmem_schedule(struct sock *sk, int size) |
| +{ |
| + int amt, status; |
| + |
| + if (size <= sk->sk_forward_alloc) |
| + return; |
| + amt = sk_mem_pages(size); |
| + sk->sk_forward_alloc += amt * SK_MEM_QUANTUM; |
| + sk_memory_allocated_add(sk, amt, &status); |
| +} |
| + |
| /* Send a fin. The caller locks the socket for us. This cannot be |
| * allowed to fail queueing a FIN frame under any circumstances. |
| */ |
| @@ -2773,11 +2788,14 @@ void tcp_send_fin(struct sock *sk) |
| } else { |
| /* Socket is locked, keep trying until memory is available. */ |
| for (;;) { |
| - skb = sk_stream_alloc_skb(sk, 0, sk->sk_allocation); |
| + skb = alloc_skb_fclone(MAX_TCP_HEADER, |
| + sk->sk_allocation); |
| if (skb) |
| break; |
| yield(); |
| } |
| + skb_reserve(skb, MAX_TCP_HEADER); |
| + sk_forced_wmem_schedule(sk, skb->truesize); |
| /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ |
| tcp_init_nondata_skb(skb, tp->write_seq, |
| TCPHDR_ACK | TCPHDR_FIN); |