Re: [PATCH net] Revert tcp: switch tcp_fastopen key generation to net_get_random_once

2015-06-18 Thread Eric Dumazet 
On Thu, 2015-06-18 at 11:32 +0200, Hannes Frederic Sowa wrote:
 Hello Christoph,

  There does not seem to be a better way to handle this. We could try
  to make the call to kmalloc and crypto_alloc_cipher during bootup, and
  then generate the random value only on-the-fly (when the first TFO-SYN
  comes in) with net_get_random_once in order to have the better entropy
  that comes with doing the late initialisation of the random value. But
  that's probably net-next material.
 
 can't we simply move the net_get_random_once to the TCP_FASTOPEN setsockopt 
 and
 sendmsg(MSG_FASTOPEN) path, so those allocations still happen in process 
 context
 but we still defer the extraction of entropy as long as posible?

Yes, I do not think this would be hard. This bug is old (3.13) and does
not seem very urgent to expedite a revert.


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Re: [PATCH net] Revert tcp: switch tcp_fastopen key generation to net_get_random_once

2015-06-18 Thread Christoph Paasch 
On 18/06/15 - 04:14:13, Eric Dumazet wrote:
 On Thu, 2015-06-18 at 11:32 +0200, Hannes Frederic Sowa wrote:
   There does not seem to be a better way to handle this. We could try
   to make the call to kmalloc and crypto_alloc_cipher during bootup, and
   then generate the random value only on-the-fly (when the first TFO-SYN
   comes in) with net_get_random_once in order to have the better entropy
   that comes with doing the late initialisation of the random value. But
   that's probably net-next material.
  
  can't we simply move the net_get_random_once to the TCP_FASTOPEN setsockopt 
  and
  sendmsg(MSG_FASTOPEN) path, so those allocations still happen in process 
  context
  but we still defer the extraction of entropy as long as posible?
 
 Yes, I do not think this would be hard. This bug is old (3.13) and does
 not seem very urgent to expedite a revert.

True, it would be simpler to call tcp_fastopen_init_key_once to the
setsocketopt() and inet_listen().

I will resubmit.


Christoph

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Re: [PATCH net] Revert tcp: switch tcp_fastopen key generation to net_get_random_once

2015-06-18 Thread Hannes Frederic Sowa 
Hello Christoph,

On Wed, 2015-06-17 at 17:28 -0700, Christoph Paasch wrote:
 This reverts commit 222e83d2e0aecb6a5e8d42b1a8d51332a1eba960.
 
 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]  04f2 88007f8838a8 8171d53a 
 880075a084a8
 [   36.009630]  880075a08000 88007f8838c8 810967d3 
 88007f883928
 [   36.011076]   88007f8838f8 81096892 
 88007f89be00
 [   36.012494] Call Trace:
 [   36.012953]  IRQ  [8171d53a] dump_stack+0x4f/0x6d
 [   36.014085]  [810967d3] ___might_sleep+0x103/0x170
 [   36.015117]  [81096892] __might_sleep+0x52/0x90
 [   36.016117]  [8118e887] kmem_cache_alloc_trace+0x47/0x190
 [   36.017266]  [81680d82] ? tcp_fastopen_reset_cipher+0x42/0x130
 [   36.018485]  [81680d82] tcp_fastopen_reset_cipher+0x42/0x130
 [   36.019679]  [81680f01] tcp_fastopen_init_key_once+0x61/0x70
 [   36.020884]  [81680f2c] __tcp_fastopen_cookie_gen+0x1c/0x60
 [   36.022058]  [816814ff] tcp_try_fastopen+0x58f/0x730
 [   36.023118]  [81671788] tcp_conn_request+0x3e8/0x7b0
 [   36.024185]  [810e3872] ? __module_text_address+0x12/0x60
 [   36.025327]  [8167b2e1] tcp_v4_conn_request+0x51/0x60
 [   36.026410]  [816727e0] tcp_rcv_state_process+0x190/0xda0
 [   36.027556]  [81661f97] ? __inet_lookup_established+0x47/0x170
 [   36.028784]  [8167c2ad] tcp_v4_do_rcv+0x16d/0x3d0
 [   36.029832]  [812e6806] ? security_sock_rcv_skb+0x16/0x20
 [   36.030936]  [8167cc8a] tcp_v4_rcv+0x77a/0x7b0
 [   36.031875]  [816af8c3] ? iptable_filter_hook+0x33/0x70
 [   36.032953]  [81657d22] ip_local_deliver_finish+0x92/0x1f0
 [   36.034065]  [81657f1a] ip_local_deliver+0x9a/0xb0
 [   36.035069]  [81657c90] ? ip_rcv+0x3d0/0x3d0
 [   36.035963]  [81657569] ip_rcv_finish+0x119/0x330
 [   36.036950]  [81657ba7] ip_rcv+0x2e7/0x3d0
 [   36.037847]  [81610652] __netif_receive_skb_core+0x552/0x930
 [   36.038994]  [81610a57] __netif_receive_skb+0x27/0x70
 [   36.040033]  [81610b72] process_backlog+0xd2/0x1f0
 [   36.041025]  [81611482] net_rx_action+0x122/0x310
 [   36.042007]  [81076743] __do_softirq+0x103/0x2f0
 [   36.042978]  [81723e3c] do_softirq_own_stack+0x1c/0x30
 
 There does not seem to be a better way to handle this. We could try
 to make the call to kmalloc and crypto_alloc_cipher during bootup, and
 then generate the random value only on-the-fly (when the first TFO-SYN
 comes in) with net_get_random_once in order to have the better entropy
 that comes with doing the late initialisation of the random value. But
 that's probably net-next material.

can't we simply move the net_get_random_once to the TCP_FASTOPEN setsockopt and
sendmsg(MSG_FASTOPEN) path, so those allocations still happen in process context
but we still defer the extraction of entropy as long as posible?

Thanks,
Hannes

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