This is a note to let you know that I've just added the patch titled
sctp: fix BH handling on socket backlog
to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sctp-fix-bh-handling-on-socket-backlog.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Aug 12 09:34:44 CEST 2016
From: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Date: Sat, 23 Jul 2016 00:32:48 -0300
Subject: sctp: fix BH handling on socket backlog
From: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
[ Upstream commit eefc1b1d105ee4d2ce907833ce675f1e9599b5e3 ]
Now that the backlog processing is called with BH enabled, we have to
disable BH before taking the socket lock via bh_lock_sock() otherwise
it may dead lock:
sctp_backlog_rcv()
bh_lock_sock(sk);
if (sock_owned_by_user(sk)) {
if (sk_add_backlog(sk, skb, sk->sk_rcvbuf))
sctp_chunk_free(chunk);
else
backloged = 1;
} else
sctp_inq_push(inqueue, chunk);
bh_unlock_sock(sk);
while sctp_inq_push() was disabling/enabling BH, but enabling BH
triggers pending softirq, which then may try to re-lock the socket in
sctp_rcv().
[ 219.187215] <IRQ>
[ 219.187217] [<ffffffff817ca3e0>] _raw_spin_lock+0x20/0x30
[ 219.187223] [<ffffffffa041888c>] sctp_rcv+0x48c/0xba0 [sctp]
[ 219.187225] [<ffffffff816e7db2>] ? nf_iterate+0x62/0x80
[ 219.187226] [<ffffffff816f1b14>] ip_local_deliver_finish+0x94/0x1e0
[ 219.187228] [<ffffffff816f1e1f>] ip_local_deliver+0x6f/0xf0
[ 219.187229] [<ffffffff816f1a80>] ? ip_rcv_finish+0x3b0/0x3b0
[ 219.187230] [<ffffffff816f17a8>] ip_rcv_finish+0xd8/0x3b0
[ 219.187232] [<ffffffff816f2122>] ip_rcv+0x282/0x3a0
[ 219.187233] [<ffffffff810d8bb6>] ? update_curr+0x66/0x180
[ 219.187235] [<ffffffff816abac4>] __netif_receive_skb_core+0x524/0xa90
[ 219.187236] [<ffffffff810d8e00>] ? update_cfs_shares+0x30/0xf0
[ 219.187237] [<ffffffff810d557c>] ? __enqueue_entity+0x6c/0x70
[ 219.187239] [<ffffffff810dc454>] ? enqueue_entity+0x204/0xdf0
[ 219.187240] [<ffffffff816ac048>] __netif_receive_skb+0x18/0x60
[ 219.187242] [<ffffffff816ad1ce>] process_backlog+0x9e/0x140
[ 219.187243] [<ffffffff816ac8ec>] net_rx_action+0x22c/0x370
[ 219.187245] [<ffffffff817cd352>] __do_softirq+0x112/0x2e7
[ 219.187247] [<ffffffff817cc3bc>] do_softirq_own_stack+0x1c/0x30
[ 219.187247] <EOI>
[ 219.187248] [<ffffffff810aa1c8>] do_softirq.part.14+0x38/0x40
[ 219.187249] [<ffffffff810aa24d>] __local_bh_enable_ip+0x7d/0x80
[ 219.187254] [<ffffffffa0408428>] sctp_inq_push+0x68/0x80 [sctp]
[ 219.187258] [<ffffffffa04190f1>] sctp_backlog_rcv+0x151/0x1c0 [sctp]
[ 219.187260] [<ffffffff81692b07>] __release_sock+0x87/0xf0
[ 219.187261] [<ffffffff81692ba0>] release_sock+0x30/0xa0
[ 219.187265] [<ffffffffa040e46d>] sctp_accept+0x17d/0x210 [sctp]
[ 219.187266] [<ffffffff810e7510>] ? prepare_to_wait_event+0xf0/0xf0
[ 219.187268] [<ffffffff8172d52c>] inet_accept+0x3c/0x130
[ 219.187269] [<ffffffff8168d7a3>] SYSC_accept4+0x103/0x210
[ 219.187271] [<ffffffff817ca2ba>] ? _raw_spin_unlock_bh+0x1a/0x20
[ 219.187272] [<ffffffff81692bfc>] ? release_sock+0x8c/0xa0
[ 219.187276] [<ffffffffa0413e22>] ? sctp_inet_listen+0x62/0x1b0 [sctp]
[ 219.187277] [<ffffffff8168f2d0>] SyS_accept+0x10/0x20
Fixes: 860fbbc343bf ("sctp: prepare for socket backlog behavior change")
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sctp/input.c | 2 ++
net/sctp/inqueue.c | 2 --
2 files changed, 2 insertions(+), 2 deletions(-)
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -328,6 +328,7 @@ int sctp_backlog_rcv(struct sock *sk, st
*/
sk = rcvr->sk;
+ local_bh_disable();
bh_lock_sock(sk);
if (sock_owned_by_user(sk)) {
@@ -339,6 +340,7 @@ int sctp_backlog_rcv(struct sock *sk, st
sctp_inq_push(inqueue, chunk);
bh_unlock_sock(sk);
+ local_bh_enable();
/* If the chunk was backloged again, don't drop refs */
if (backloged)
--- a/net/sctp/inqueue.c
+++ b/net/sctp/inqueue.c
@@ -89,12 +89,10 @@ void sctp_inq_push(struct sctp_inq *q, s
* Eventually, we should clean up inqueue to not rely
* on the BH related data structures.
*/
- local_bh_disable();
list_add_tail(&chunk->list, &q->in_chunk_list);
if (chunk->asoc)
chunk->asoc->stats.ipackets++;
q->immediate.func(&q->immediate);
- local_bh_enable();
}
/* Peek at the next chunk on the inqeue. */
Patches currently in stable-queue which might be from marcelo.leitner@xxxxxxxxx are
queue-4.7/sctp-fix-bh-handling-on-socket-backlog.patch
queue-4.7/net-sctp-terminate-rhashtable-walk-correctly.patch
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