path: root/net
diff options
authorEric Dumazet <edumazet@google.com>2015-04-21 18:32:24 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-05-06 21:56:20 +0200
commitaac9fda375bbe75e0b8c033874af25e0f7f5a3a4 (patch)
tree2937341d32859675019e9a5d34739f66b4f8e69a /net
parentfb138c4699c94b16bf9400394142c6d86fe70226 (diff)
tcp: fix possible deadlock in tcp_send_fin()
[ 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>
Diffstat (limited to 'net')
1 files changed, 19 insertions, 1 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 7681a1bbd97f..546371973b9a 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2571,6 +2571,21 @@ 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.
@@ -2593,11 +2608,14 @@ 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)
+ 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,