@@ -2675,6 +2675,21 @@ 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.
*/
@@ -2697,11 +2712,14 @@ 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);
This is a note to let you know that I have just added a patch titled tcp: fix possible deadlock in tcp_send_fin() to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt11. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 049ba12387d9fb07330bbebf18cce4ec0f5acaf1 Mon Sep 17 00:00:00 2001 From: Eric Dumazet <edumazet@google.com> Date: Tue, 21 Apr 2015 18:32:24 -0700 Subject: tcp: fix possible deadlock in tcp_send_fin() commit d83769a580f1132ac26439f50068a29b02be535e upstream. 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: Luis Henriques <luis.henriques@canonical.com> --- net/ipv4/tcp_output.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)