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);
--
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