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SubjectRe: [PATCH v2 00/11] tty: Fix buffer work access-after-free
On Fri, Dec 14, 2012 at 1:22 PM, Peter Hurley <peter@hurleysoftware.com> wrote:
> I wasn't sure if this is something to squeeze into 3.8, so don't yell
> if not. At least Sasha can apply this and re-test against trinity.
>
> Changes in v2:
>
> - Please review "tty: Don't flush buffer when closing ldisc".
> This patch replaces the earlier
> "tty: Don't reschedule buffer work while closing". The text of
> this commit details why not calling n_tty_flush_buffer() is the
> correct thing to do, so I won't repeat it here.
>
> - Jiri's debug patch "tty: debug buffer work race with tty free"
> has been included (albeit a slightly different version)
> Jiri, please sign off (or point out what you'd like changed).
>
> - The test jig has been included in the commit message for
> "tty: Don't flush buffer when closing ldisc" as Alan requested.
>
> - Ilya Zykov was added as the Signed-off-by: for the test jig in
> that same commit message.
>
> - Sasha Levin was added as the Reported-by: in that same patch.
>
>
> This patch series addresses the causes of flush_to_ldisc accessing
> the tty after freeing.
>
> The most common cause stems from the n_tty_close() path spuriously
> scheduling buffer work, when the ldisc has already been halted.
> This is fixed in 'tty: Don't flush buffer when closing ldisc'

I'm still seeing that warning with the new patch series:

[ 549.561769] ------------[ cut here ]------------
[ 549.598755] WARNING: at drivers/tty/n_tty.c:160 n_tty_set_room+0xff/0x130()
[ 549.604058] scheduling buffer work for halted ldisc
[ 549.607741] Pid: 9417, comm: trinity-child28 Tainted: G D W
3.7.0-next-20121217-sasha-00023-g8689ef9 #219
[ 549.652580] Call Trace:
[ 549.662754] [<ffffffff81c432cf>] ? n_tty_set_room+0xff/0x130
[ 549.665458] [<ffffffff8110cae7>] warn_slowpath_common+0x87/0xb0
[ 549.668257] [<ffffffff8110cb71>] warn_slowpath_fmt+0x41/0x50
[ 549.671007] [<ffffffff81c432cf>] n_tty_set_room+0xff/0x130
[ 549.673268] [<ffffffff81c44597>] reset_buffer_flags+0x137/0x150
[ 549.675607] [<ffffffff81c45b71>] n_tty_open+0x131/0x1c0
[ 549.677699] [<ffffffff81c47824>] tty_ldisc_open.isra.5+0x54/0x70
[ 549.680147] [<ffffffff81c482bf>] tty_ldisc_hangup+0x11f/0x1e0
[ 549.682409] [<ffffffff81c3fa17>] __tty_hangup+0x137/0x440
[ 549.684634] [<ffffffff81c3fd49>] tty_vhangup+0x9/0x10
[ 549.686443] [<ffffffff81c4a42c>] pty_close+0x14c/0x160
[ 549.688446] [<ffffffff81c41225>] tty_release+0xd5/0x490
[ 549.690460] [<ffffffff8127d8a2>] __fput+0x122/0x250
[ 549.692577] [<ffffffff8127d9d9>] ____fput+0x9/0x10
[ 549.694534] [<ffffffff811348c2>] task_work_run+0xb2/0xf0
[ 549.696349] [<ffffffff81113c6d>] do_exit+0x36d/0x580
[ 549.698286] [<ffffffff8107d964>] ? syscall_trace_enter+0x24/0x2e0
[ 549.702729] [<ffffffff81113f4a>] do_group_exit+0x8a/0xc0
[ 549.706775] [<ffffffff81113f92>] sys_exit_group+0x12/0x20
[ 549.711088] [<ffffffff83cfab18>] tracesys+0xe1/0xe6
[ 549.728001] ---[ end trace 73eb41728f11f87e ]---


Thanks,
Sasha


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