[MPTCP] Re: [PATCH mptcp-net] mptcp: fix memory accounting on allocation error

[Christoph Paasch <cpaasch at apple.com>]

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On 02/19/21 - 19:42, Paolo Abeni wrote:
> 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 <cpaasch(a)apple.com>
> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/136
> Fixes: 724cfd2ee8aa ("mptcp: allocate TX skbs in msk context")
> Signed-off-by: Paolo Abeni <pabeni(a)redhat.com>
> ---
> @Christoph: could you please give this one a spin in your
> testbed vs the repro?

Works for me!!! That must have been hell of a good beer! :-)


Christoph