Messages in this thread | | | Date | Thu, 7 Aug 2014 13:22:01 -0700 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] tty: Fix potential use after free in release_one_tty |
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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 <gorcunov@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 <xemul@parallels.com> > CC: Jiri Slaby <jslaby@suse.cz> > CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Signed-off-by: Cyrill Gorcunov <gorcunov@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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