netdev - Re: [PATCH 3/6] can: slcan: Fix use-after-free Read in slcan

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Date:   Tue, 3 Dec 2019 12:53:54 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Oliver Hartkopp <socketcan@...tkopp.net>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, linux-can@...r.kernel.org,
        kernel@...gutronix.de, Jouni Hogander <jouni.hogander@...kie.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        linux-stable <stable@...r.kernel.org>
Subject: Re: [PATCH 3/6] can: slcan: Fix use-after-free Read in slcan_open

On 12/3/19 12:21 PM, Oliver Hartkopp wrote:
> 
> 
> On 03/12/2019 11.47, Marc Kleine-Budde wrote:
>> From: Jouni Hogander <jouni.hogander@...kie.com>
>>
>> Slcan_open doesn't clean-up device which registration failed from the
>> slcan_devs device list. On next open this list is iterated and freed
>> device is accessed. Fix this by calling slc_free_netdev in error path.
>>
>> Driver/net/can/slcan.c is derived from slip.c. Use-after-free error was
>> identified in slip_open by syzboz. Same bug is in slcan.c. Here is the
>> trace from the Syzbot slip report:
>>
>> __dump_stack lib/dump_stack.c:77 [inline]
>> dump_stack+0x197/0x210 lib/dump_stack.c:118
>> print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
>> __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
>> kasan_report+0x12/0x20 mm/kasan/common.c:634
>> __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
>> sl_sync drivers/net/slip/slip.c:725 [inline]
>> slip_open+0xecd/0x11b7 drivers/net/slip/slip.c:801
>> tty_ldisc_open.isra.0+0xa3/0x110 drivers/tty/tty_ldisc.c:469
>> tty_set_ldisc+0x30e/0x6b0 drivers/tty/tty_ldisc.c:596
>> tiocsetd drivers/tty/tty_io.c:2334 [inline]
>> tty_ioctl+0xe8d/0x14f0 drivers/tty/tty_io.c:2594
>> vfs_ioctl fs/ioctl.c:46 [inline]
>> file_ioctl fs/ioctl.c:509 [inline]
>> do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
>> ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
>> __do_sys_ioctl fs/ioctl.c:720 [inline]
>> __se_sys_ioctl fs/ioctl.c:718 [inline]
>> __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
>> do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
>> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> Fixes: ed50e1600b44 ("slcan: Fix memory leak in error path")
>> Cc: Wolfgang Grandegger <wg@...ndegger.com>
>> Cc: Marc Kleine-Budde <mkl@...gutronix.de>
>> Cc: David Miller <davem@...emloft.net>
>> Cc: Oliver Hartkopp <socketcan@...tkopp.net>
>> Cc: Lukas Bulwahn <lukas.bulwahn@...il.com>
>> Signed-off-by: Jouni Hogander <jouni.hogander@...kie.com>
>> Cc: linux-stable <stable@...r.kernel.org> # >= v5.4
> 
> I think this problem existed from the initial commit in 2010 and is not 
> restricted to >= v5.4
> 
> Together with commit commit ed50e1600b4483c049 ("slcan: Fix memory leak 
> in error path") from Jouni Hogander.

Yes, both patches shoud be backported:

ed50e1600b44 slcan: Fix memory leak in error path
9ebd796e2400 can: slcan: Fix use-after-free Read in slcan_open

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |



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