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.duma...@gmail.com>
> Cc: Hannes Frederic Sowa <han...@stressinduktion.org>
> Fixes: 222e83d2e0ae ("tcp: switch tcp_fastopen key generation to
> net_get_random_once")
> Signed-off-by: Christoph Paasch <cpaa...@apple.com>
> ---
Acked-by: Eric Dumazet <eduma...@google.com>
Thanks Christoph.
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