From 77c6eed1af0dcd2aa8c3d16c2631162eb5d30908 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Mon, 8 Mar 2021 13:38:16 +0000 Subject: [PATCH] mptcp: fix memory accounting on allocation error In case of memory pressure the MPTCP xmit path keeps at most a single skb in the tx cache, eventually freeing additional ones. The associated counter for forward memory is not update accordingly, and that causes the following splat: WARNING: CPU: 0 PID: 12 at net/core/stream.c:208 sk_stream_kill_queues+0x3ca/0x530 net/core/stream.c:208 Modules linked in: CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.11.0-rc2 #59 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 Workqueue: events mptcp_worker RIP: 0010:sk_stream_kill_queues+0x3ca/0x530 net/core/stream.c:208 Code: 03 0f b6 04 02 84 c0 74 08 3c 03 0f 8e 63 01 00 00 8b ab 00 01 00 00 e9 60 ff ff ff e8 2f 24 d3 fe 0f 0b eb 97 e8 26 24 d3 fe <0f> 0b eb a0 e8 1d 24 d3 fe 0f 0b e9 a5 fe ff ff 4c 89 e7 e8 0e d0 RSP: 0018:ffffc900000c7bc8 EFLAGS: 00010293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff88810030ac40 RSI: ffffffff8262ca4a RDI: 0000000000000003 RBP: 0000000000000d00 R08: 0000000000000000 R09: ffffffff85095aa7 R10: ffffffff8262c9ea R11: 0000000000000001 R12: ffff888108908100 R13: ffffffff85095aa0 R14: ffffc900000c7c48 R15: 1ffff92000018f85 FS: 0000000000000000(0000) GS:ffff88811b200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa7444baef8 CR3: 0000000035ee9005 CR4: 0000000000170ef0 Call Trace: __mptcp_destroy_sock+0x4a7/0x6c0 net/mptcp/protocol.c:2547 mptcp_worker+0x7dd/0x1610 net/mptcp/protocol.c:2272 process_one_work+0x896/0x1170 kernel/workqueue.c:2275 worker_thread+0x605/0x1350 kernel/workqueue.c:2421 kthread+0x344/0x410 kernel/kthread.c:292 ret_from_fork+0x22/0x30 arch/x86/entry/entry_64.S:296 At close time, as reported by syzkaller/Christoph. This change address the issue properly updating the fwd allocated memory counter in the error path. Reported-by: Christoph Paasch Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/136 Fixes: 724cfd2ee8aa ("mptcp: allocate TX skbs in msk context") Reviewed-by: Mat Martineau Signed-off-by: Paolo Abeni --- net/mptcp/protocol.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 7362a536cbc01..aa59101ffe546 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1189,6 +1189,7 @@ static bool mptcp_tx_cache_refill(struct sock *sk, int size, */ while (skbs->qlen > 1) { skb = __skb_dequeue_tail(skbs); + *total_ts -= skb->truesize; __kfree_skb(skb); } return skbs->qlen > 0;