On Thu, Aug 07, 2014 at 01:34:28PM +0400, Cyrill Gorcunov wrote:
> On Thu, Aug 07, 2014 at 01:18:12PM +0400, Cyrill Gorcunov wrote:
> > > mod = driver->owner;
> > > tty_driver_kref_put(driver);
> > > module_put(mod);
> > >
> > > Check the upstream whether the same issue exists there.
> >
> > Same in tty.git
> >
> > static void release_one_tty(struct work_struct *work)
> > {
> ---
> From: Cyrill Gorcunov <gorcu...@gmail.com>
> Subject: tty: Fix potential use after free in release_one_tty
>
> In case if we're releasing the last tty reference the following
> call sequence is possible
>
> tty_driver_kref_put
> destruct_tty_driver
> kfree(driver);
>
> where @driver is used in next module_put call, which leads to
>
> | [ 285.964007] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
> | [ 285.964007] Workqueue: events release_one_tty
> | [ 285.964007] task: ffff8800cc7ea5f0 ti: ffff8800cb800000 task.ti:
> ffff8800cb800000
> | [ 285.964007] RIP: 0010:[<ffffffff810aeaf5>] [<ffffffff810aeaf5>]
> module_put+0x24/0xf4
> | [ 285.964007] RSP: 0018:ffff8800cb801d48 EFLAGS: 00010213
> | [ 285.964007] RAX: ffff8800cb801fd8 RBX: ffff8800ca3429d0 RCX:
> ffff8800cb1db400
> | [ 285.964007] RDX: 0000000000000000 RSI: ffffffff817349c1 RDI:
> 0000000000000001
> | [ 285.964007] RBP: ffff8800cb801d60 R08: ffff8800cd632b40 R09:
> 0000000000000000
> | [ 285.964007] R10: 00000000ffffffff R11: ffff88011f40a000 R12:
> 6b6b6b6b6b6b6b6b
> | [ 285.964007] R13: ffff8800ca342520 R14: 0000000000000000 R15:
> ffff88011f5d8200
> | [ 285.964007] FS: 0000000000000000(0000) GS:ffff88011f400000(0000)
> knlGS:0000000000000000
> | [ 285.964007] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> | [ 285.964007] CR2: 00007faf5229d090 CR3: 0000000001c0b000 CR4:
> 00000000000006f0
> | [ 285.964007] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> 0000000000000000
> | [ 285.964007] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
> 0000000000000400
> | [ 285.964007] Stack:
> | [ 285.964007] ffff8800ca3429d0 ffff8800ca342a30 ffff8800ca342520
> ffff8800cb801d88
> | [ 285.964007] ffffffff8146554a ffff8800cc77cc78 ffff8800ca3429d0
> ffff88011f5d3800
> | [ 285.964007] ffff8800cb801e08 ffffffff810683c1 ffffffff810682ff
> 0000000000000046
> | [ 285.964007] Call Trace:
> | [ 285.964007] [<ffffffff8146554a>] release_one_tty+0x54/0xa3
> | [ 285.964007] [<ffffffff810683c1>] process_one_work+0x223/0x404
> | [ 285.964007] [<ffffffff810682ff>] ? process_one_work+0x161/0x404
> | [ 285.964007] [<ffffffff81068971>] worker_thread+0x136/0x205
> | [ 285.964007] [<ffffffff8106883b>] ? rescuer_thread+0x26a/0x26a
> | [ 285.964007] [<ffffffff8106e5bf>] kthread+0xa2/0xaa
> | [ 285.964007] [<ffffffff810a4586>] ? trace_hardirqs_on_caller+0x16/0x1eb
> | [ 285.964007] [<ffffffff8106e51d>] ? __kthread_parkme+0x65/0x65
> | [ 285.964007] [<ffffffff8173f59c>] ret_from_fork+0x7c/0xb0
> | [ 285.964007] [<ffffffff8106e51d>] ? __kthread_parkme+0x65/0x65
> | [ 285.964007] Code: 09 00 5b 41 5c 5d c3 0f 1f 44 00 00 55 48 85 ff 48 89
> e5 41 55 41 54 49 89 fc 53 0f 84 d3 00
> | 00 00 bf 01 00 00 00 e8 d0 a1 fc ff <49> 8b 84 24 50 02 00 00 65 48 ff 40
> 08 4c 8b 6d 08 0f 1f 44 00
>
> so simply keep a local reference to the module owner and
> use it later.
>
> (Note I hit the bug on custom kernel but I think vanilla one suffers
> the same problem).
>
> CC: Pavel Emelyanov <xe...@parallels.com>
> CC: Jiri Slaby <jsl...@suse.cz>
> CC: Greg Kroah-Hartman <gre...@linuxfoundation.org>
> Signed-off-by: Cyrill Gorcunov <gorcu...@openvz.org>
> ---
> drivers/tty/tty_io.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.git/drivers/tty/tty_io.c
> ===================================================================
> --- linux-2.6.git.orig/drivers/tty/tty_io.c
> +++ linux-2.6.git/drivers/tty/tty_io.c
> @@ -1559,13 +1559,14 @@ static void release_one_tty(struct work_
> struct tty_struct *tty =
> container_of(work, struct tty_struct, hangup_work);
> struct tty_driver *driver = tty->driver;
> + struct module *owner = driver->owner;
>
> if (tty->ops->cleanup)
> tty->ops->cleanup(tty);
>
> tty->magic = 0;
> tty_driver_kref_put(driver);
> - module_put(driver->owner);
> + module_put(owner);
>
> spin_lock(&tty_files_lock);
> list_del_init(&tty->tty_files);
Looks good, thanks, can you resend it in a format I can apply it in (one
that doesn't require me to edit it by hand)? Then I'll be glad to queue
it up after 3.17-rc1 is out.
thanks,
greg k-h
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