From: Joshua Kinard <kumba@gentoo•org>
To: Daniel Borkmann <dborkman@redhat•com>, davem@davemloft•net
Cc: netdev@vger•kernel.org, linux-sctp@vger•kernel.org,
Vlad Yasevich <vyasevic@redhat•com>
Subject: Re: [PATCH net] net: sctp: cache auth_enable per endpoint
Date: Thu, 17 Apr 2014 21:54:10 -0400 [thread overview]
Message-ID: <535085C2.8040409@gentoo.org> (raw)
In-Reply-To: <1397748410-1983-1-git-send-email-dborkman@redhat.com>
On 04/17/2014 11:26, Daniel Borkmann wrote:
> From: Vlad Yasevich <vyasevic@redhat•com>
>
> Currently, it is possible to create an SCTP socket, then switch
> auth_enable via sysctl setting to 1 and crash the system on connect:
>
> Oops[#1]:
> CPU: 0 PID: 0 Comm: swapper Not tainted 3.14.1-mipsgit-20140415 #1
> task: ffffffff8056ce80 ti: ffffffff8055c000 task.ti: ffffffff8055c000
> [...]
> Call Trace:
> [<ffffffff8043c4e8>] sctp_auth_asoc_set_default_hmac+0x68/0x80
> [<ffffffff8042b300>] sctp_process_init+0x5e0/0x8a4
> [<ffffffff8042188c>] sctp_sf_do_5_1B_init+0x234/0x34c
> [<ffffffff804228c8>] sctp_do_sm+0xb4/0x1e8
> [<ffffffff80425a08>] sctp_endpoint_bh_rcv+0x1c4/0x214
> [<ffffffff8043af68>] sctp_rcv+0x588/0x630
> [<ffffffff8043e8e8>] sctp6_rcv+0x10/0x24
> [<ffffffff803acb50>] ip6_input+0x2c0/0x440
> [<ffffffff8030fc00>] __netif_receive_skb_core+0x4a8/0x564
> [<ffffffff80310650>] process_backlog+0xb4/0x18c
> [<ffffffff80313cbc>] net_rx_action+0x12c/0x210
> [<ffffffff80034254>] __do_softirq+0x17c/0x2ac
> [<ffffffff800345e0>] irq_exit+0x54/0xb0
> [<ffffffff800075a4>] ret_from_irq+0x0/0x4
> [<ffffffff800090ec>] rm7k_wait_irqoff+0x24/0x48
> [<ffffffff8005e388>] cpu_startup_entry+0xc0/0x148
> [<ffffffff805a88b0>] start_kernel+0x37c/0x398
> Code: dd0900b8 000330f8 0126302d <dcc60000> 50c0fff1 0047182a a48306a0
> 03e00008 00000000
> ---[ end trace b530b0551467f2fd ]---
> Kernel panic - not syncing: Fatal exception in interrupt
>
> What happens while auth_enable=0 in that case is, that
> ep->auth_hmacs is initialized to NULL in sctp_auth_init_hmacs()
> when endpoint is being created.
>
> After that point, if an admin switches over to auth_enable=1,
> the machine can crash due to NULL pointer dereference during
> reception of an INIT chunk. When we enter sctp_process_init()
> via sctp_sf_do_5_1B_init() in order to respond to an INIT chunk,
> the INIT verification succeeds and while we walk and process
> all INIT params via sctp_process_param() we find that
> net->sctp.auth_enable is set, therefore do not fall through,
> but invoke sctp_auth_asoc_set_default_hmac() instead, and thus,
> dereference what we have set to NULL during endpoint
> initialization phase.
>
> The fix is to make auth_enable immutable by caching its value
> during endpoint initialization, so that its original value is
> being carried along until destruction. The bug seems to originate
> from the very first days.
>
> Fix in joint work with Daniel Borkmann.
>
> Reported-by: Joshua Kinard <kumba@gentoo•org>
> Signed-off-by: Vlad Yasevich <vyasevic@redhat•com>
> Signed-off-by: Daniel Borkmann <dborkman@redhat•com>
This solves the problem for me, thanks!
Tested-by: Joshua Kinard <kumba@gentoo•org>
next prev parent reply other threads:[~2014-04-18 2:00 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-17 15:26 [PATCH net] net: sctp: cache auth_enable per endpoint Daniel Borkmann
2014-04-17 20:44 ` Neil Horman
2014-04-18 1:54 ` Joshua Kinard [this message]
2014-04-18 22:41 ` David Miller
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