[PATCH 3.10 127/319] ALSA: timer: fix NULL pointer dereference on memory allocation failure

Willy Tarreau
2017-02-05T19:28:07Z

From: Vegard Nossum <vegard.nossum@oracle.com>

commit 8ddc05638ee42b18ba4fe99b5fb647fa3ad20456 upstream.

I hit this with syzkaller:

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 1327 Comm: a.out Not tainted 4.8.0-rc2+ #190
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
task: ffff88011278d600 task.stack: ffff8801120c0000
RIP: 0010:[<ffffffff82c8ba07>] [<ffffffff82c8ba07>] snd_hrtimer_start+0x77/0x100
RSP: 0018:ffff8801120c7a60 EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000007
RDX: 0000000000000009 RSI: 1ffff10023483091 RDI: 0000000000000048
RBP: ffff8801120c7a78 R08: ffff88011a5cf768 R09: ffff88011a5ba790
R10: 0000000000000002 R11: ffffed00234b9ef1 R12: ffff880114843980
R13: ffffffff84213c00 R14: ffff880114843ab0 R15: 0000000000000286
FS: 00007f72958f3700(0000) GS:ffff88011aa00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000603001 CR3: 00000001126ab000 CR4: 00000000000006f0
Stack:
ffff880114843980 ffff880111eb2dc0 ffff880114843a34 ffff8801120c7ad0
ffffffff82c81ab1 0000000000000000 ffffffff842138e0 0000000100000000
ffff880111eb2dd0 ffff880111eb2dc0 0000000000000001 ffff880111eb2dc0
Call Trace:
[<ffffffff82c81ab1>] snd_timer_start1+0x331/0x670
[<ffffffff82c85bfd>] snd_timer_start+0x5d/0xa0
[<ffffffff82c8795e>] snd_timer_user_ioctl+0x88e/0x2830
[<ffffffff8159f3a0>] ? __follow_pte.isra.49+0x430/0x430
[<ffffffff82c870d0>] ? snd_timer_pause+0x80/0x80
[<ffffffff815a26fa>] ? do_wp_page+0x3aa/0x1c90
[<ffffffff8132762f>] ? put_prev_entity+0x108f/0x21a0
[<ffffffff82c870d0>] ? snd_timer_pause+0x80/0x80
[<ffffffff816b0733>] do_vfs_ioctl+0x193/0x1050
[<ffffffff813510af>] ? cpuacct_account_field+0x12f/0x1a0
[<ffffffff816b05a0>] ? ioctl_preallocate+0x200/0x200
[<ffffffff81002f2f>] ? syscall_trace_enter+0x3cf/0xdb0
[<ffffffff815045ba>] ? __context_tracking_exit.part.4+0x9a/0x1e0
[<ffffffff81002b60>] ? exit_to_usermode_loop+0x190/0x190
[<ffffffff82001a97>] ? check_preemption_disabled+0x37/0x1e0
[<ffffffff81d93889>] ? security_file_ioctl+0x89/0xb0
[<ffffffff816b167f>] SyS_ioctl+0x8f/0xc0
[<ffffffff816b15f0>] ? do_vfs_ioctl+0x1050/0x1050
[<ffffffff81005524>] do_syscall_64+0x1c4/0x4e0
[<ffffffff83c32b2a>] entry_SYSCALL64_slow_path+0x25/0x25
Code: c7 c7 c4 b9 c8 82 48 89 d9 4c 89 ee e8 63 88 7f fe e8 7e 46 7b fe 48 8d 7b 48 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 04 84 c0 7e 65 80 7b 48 00 74 0e e8 52 46
RIP [<ffffffff82c8ba07>] snd_hrtimer_start+0x77/0x100
RSP <ffff8801120c7a60>
---[ end trace 5955b08db7f2b029 ]---

This can happen if snd_hrtimer_open() fails to allocate memory and
returns an error, which is currently not checked by snd_timer_open():

ioctl(SNDRV_TIMER_IOCTL_SELECT)
- snd_timer_user_tselect()
- snd_timer_close()
- snd_hrtimer_close()
- (struct snd_timer *) t->private_data = NULL
- snd_timer_open()
- snd_hrtimer_open()
- kzalloc() fails; t->private_data is still NULL

ioctl(SNDRV_TIMER_IOCTL_START)
- snd_timer_user_start()
- snd_timer_start()
- snd_timer_start1()
- snd_hrtimer_start()
- t->private_data == NULL // boom

[js] no put_device in 3.12 yet

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
sound/core/timer.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/sound/core/timer.c b/sound/core/timer.c
index f297eac..749857a 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -291,8 +291,19 @@ int snd_timer_open(struct snd_timer_instance **ti,
}
timeri->slave_class = tid->dev_sclass;
timeri->slave_id = slave_id;
- if (list_empty(&timer->open_list_head) && timer->hw.open)
- timer->hw.open(timer);
+
+ if (list_empty(&timer->open_list_head) && timer->hw.open) {
+ int err = timer->hw.open(timer);
+ if (err) {
+ kfree(timeri->owner);
+ kfree(timeri);
+
+ module_put(timer->module);
+ mutex_unlock(&register_mutex);
+ return err;
+ }
+ }
+
list_add_tail(&timeri->open_list, &timer->open_list_head);
snd_timer_check_master(timeri);
mutex_unlock(&register_mutex);
--
2.8.0.rc2.1.gbe9624a