netdev - Re: [PATCH net v2] tcp: Do not call tcp_fastopen_reset

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Date:	Fri, 19 Jun 2015 01:01:51 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Christoph Paasch <cpaasch@...le.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Hannes Frederic Sowa <hannes@...essinduktion.org>
Subject: Re: [PATCH net v2] tcp: Do not call tcp_fastopen_reset_cipher from
 interrupt context

On Thu, 2015-06-18 at 09:15 -0700, Christoph Paasch wrote:
> tcp_fastopen_reset_cipher really cannot be called from interrupt
> context. It allocates the tcp_fastopen_context with GFP_KERNEL and
> calls crypto_alloc_cipher, which allocates all kind of stuff with
> GFP_KERNEL.
> 
> Thus, we might sleep when the key-generation is triggered by an
> incoming TFO cookie-request which would then happen in interrupt-
> context, as shown by enabling CONFIG_DEBUG_ATOMIC_SLEEP:
> 
> [   36.001813] BUG: sleeping function called from invalid context at mm/slub.c:1266
> [   36.003624] in_atomic(): 1, irqs_disabled(): 0, pid: 1016, name: packetdrill
> [   36.004859] CPU: 1 PID: 1016 Comm: packetdrill Not tainted 4.1.0-rc7 #14
> [   36.006085] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
> [   36.008250]  00000000000004f2 ffff88007f8838a8 ffffffff8171d53a ffff880075a084a8
> [   36.009630]  ffff880075a08000 ffff88007f8838c8 ffffffff810967d3 ffff88007f883928
> [   36.011076]  0000000000000000 ffff88007f8838f8 ffffffff81096892 ffff88007f89be00
> [   36.012494] Call Trace:
> [   36.012953]  <IRQ>  [<ffffffff8171d53a>] dump_stack+0x4f/0x6d
> [   36.014085]  [<ffffffff810967d3>] ___might_sleep+0x103/0x170
> [   36.015117]  [<ffffffff81096892>] __might_sleep+0x52/0x90
> [   36.016117]  [<ffffffff8118e887>] kmem_cache_alloc_trace+0x47/0x190
> [   36.017266]  [<ffffffff81680d82>] ? tcp_fastopen_reset_cipher+0x42/0x130
> [   36.018485]  [<ffffffff81680d82>] tcp_fastopen_reset_cipher+0x42/0x130
> [   36.019679]  [<ffffffff81680f01>] tcp_fastopen_init_key_once+0x61/0x70
> [   36.020884]  [<ffffffff81680f2c>] __tcp_fastopen_cookie_gen+0x1c/0x60
> [   36.022058]  [<ffffffff816814ff>] tcp_try_fastopen+0x58f/0x730
> [   36.023118]  [<ffffffff81671788>] tcp_conn_request+0x3e8/0x7b0
> [   36.024185]  [<ffffffff810e3872>] ? __module_text_address+0x12/0x60
> [   36.025327]  [<ffffffff8167b2e1>] tcp_v4_conn_request+0x51/0x60
> [   36.026410]  [<ffffffff816727e0>] tcp_rcv_state_process+0x190/0xda0
> [   36.027556]  [<ffffffff81661f97>] ? __inet_lookup_established+0x47/0x170
> [   36.028784]  [<ffffffff8167c2ad>] tcp_v4_do_rcv+0x16d/0x3d0
> [   36.029832]  [<ffffffff812e6806>] ? security_sock_rcv_skb+0x16/0x20
> [   36.030936]  [<ffffffff8167cc8a>] tcp_v4_rcv+0x77a/0x7b0
> [   36.031875]  [<ffffffff816af8c3>] ? iptable_filter_hook+0x33/0x70
> [   36.032953]  [<ffffffff81657d22>] ip_local_deliver_finish+0x92/0x1f0
> [   36.034065]  [<ffffffff81657f1a>] ip_local_deliver+0x9a/0xb0
> [   36.035069]  [<ffffffff81657c90>] ? ip_rcv+0x3d0/0x3d0
> [   36.035963]  [<ffffffff81657569>] ip_rcv_finish+0x119/0x330
> [   36.036950]  [<ffffffff81657ba7>] ip_rcv+0x2e7/0x3d0
> [   36.037847]  [<ffffffff81610652>] __netif_receive_skb_core+0x552/0x930
> [   36.038994]  [<ffffffff81610a57>] __netif_receive_skb+0x27/0x70
> [   36.040033]  [<ffffffff81610b72>] process_backlog+0xd2/0x1f0
> [   36.041025]  [<ffffffff81611482>] net_rx_action+0x122/0x310
> [   36.042007]  [<ffffffff81076743>] __do_softirq+0x103/0x2f0
> [   36.042978]  [<ffffffff81723e3c>] do_softirq_own_stack+0x1c/0x30
> 
> This patch moves the call to tcp_fastopen_init_key_once to the places
> where a listener socket creates its TFO-state, which always happens in
> user-context (either from the setsockopt, or implicitly during the
> listen()-call)
> 
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> Cc: Hannes Frederic Sowa <hannes@...essinduktion.org>
> Fixes: 222e83d2e0ae ("tcp: switch tcp_fastopen key generation to net_get_random_once")
> Signed-off-by: Christoph Paasch <cpaasch@...le.com>
> ---

Acked-by: Eric Dumazet <edumazet@...gle.com>

Thanks Christoph.


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