[alsa-devel] KASAN: use-after-free Read in snd_pcm_timer_resolution
Hello,
syzbot hit the following crash on upstream commit 0b412605ef5f5c64b31f19e2910b1d5eba9929c3 (Thu Mar 29 01:07:23 2018 +0000) Merge tag 'drm-fixes-for-v4.16-rc8' of git://people.freedesktop.org/~airlied/linux syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=8e62ff4e07aa2ce87826
So far this crash happened 3 times on upstream. C reproducer: https://syzkaller.appspot.com/x/repro.c?id=6219387178582016 syzkaller reproducer: https://syzkaller.appspot.com/x/repro.syz?id=5176598244360192 Raw console output: https://syzkaller.appspot.com/x/log.txt?id=5815694612496384 Kernel config: https://syzkaller.appspot.com/x/.config?id=-8440362230543204781 compiler: gcc (GCC) 7.1.1 20170620
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+8e62ff4e07aa2ce87826@syzkaller.appspotmail.com It will help syzbot understand when the bug is fixed. See footer for details. If you forward the report, please keep this part and the footer.
================================================================== BUG: KASAN: use-after-free in snd_pcm_timer_resolution+0xa3/0xc0 sound/core/pcm_timer.c:72 Read of size 4 at addr ffff8801bdd58490 by task syzkaller702213/13238
CPU: 0 PID: 13238 Comm: syzkaller702213 Not tainted 4.16.0-rc7+ #370 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report+0x23c/0x360 mm/kasan/report.c:412 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432 snd_pcm_timer_resolution+0xa3/0xc0 sound/core/pcm_timer.c:72 snd_timer_resolution sound/core/timer.c:439 [inline] snd_timer_notify1+0x10f/0x400 sound/core/timer.c:462 snd_timer_start1+0x586/0x8f0 sound/core/timer.c:522 snd_timer_start+0x5d/0xa0 sound/core/timer.c:634 snd_timer_user_start.isra.12+0xde/0x130 sound/core/timer.c:1878 snd_timer_user_continue sound/core/timer.c:1902 [inline] __snd_timer_user_ioctl+0x1771/0x2c10 sound/core/timer.c:1977 snd_timer_user_ioctl+0x5f/0x7d sound/core/timer.c:1992 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4453c9 RSP: 002b:00007ffd46abffe8 EFLAGS: 00000217 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004453c9 RDX: 00000000004453c9 RSI: 00000000000054a2 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000046ac0168 R09: 0000000046ac0168 R10: 0000000046ac0168 R11: 0000000000000217 R12: 00000000000142ea R13: 0000000000402c90 R14: 00000000006d1440 R15: 0000000000000000
Allocated by task 13234: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552 kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3608 kmalloc include/linux/slab.h:512 [inline] kzalloc include/linux/slab.h:701 [inline] snd_pcm_attach_substream+0x3c5/0xb60 sound/core/pcm.c:1006 snd_pcm_open_substream+0x95/0x3b0 sound/core/pcm_native.c:2372 snd_pcm_oss_open_file sound/core/oss/pcm_oss.c:2309 [inline] snd_pcm_oss_open+0x7cf/0x1540 sound/core/oss/pcm_oss.c:2391 soundcore_open+0x321/0x630 sound/sound_core.c:597 chrdev_open+0x257/0x730 fs/char_dev.c:417 do_dentry_open+0x667/0xd40 fs/open.c:752 vfs_open+0x107/0x220 fs/open.c:866 do_last fs/namei.c:3379 [inline] path_openat+0x1151/0x3530 fs/namei.c:3519 do_filp_open+0x25b/0x3b0 fs/namei.c:3554 do_sys_open+0x502/0x6d0 fs/open.c:1059 SYSC_openat fs/open.c:1086 [inline] SyS_openat+0x30/0x40 fs/open.c:1080 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7
Freed by task 13234: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527 __cache_free mm/slab.c:3486 [inline] kfree+0xd9/0x260 mm/slab.c:3801 snd_pcm_detach_substream+0x134/0x290 sound/core/pcm.c:1057 snd_pcm_release_substream.part.44+0x23d/0x300 sound/core/pcm_native.c:2361 snd_pcm_release_substream+0x59/0x70 sound/core/pcm_native.c:2362 snd_pcm_oss_release_file.part.18+0x71/0xa0 sound/core/oss/pcm_oss.c:2268 snd_pcm_oss_release_file sound/core/oss/pcm_oss.c:2263 [inline] snd_pcm_oss_release+0x104/0x280 sound/core/oss/pcm_oss.c:2448 __fput+0x327/0x7e0 fs/file_table.c:209 ____fput+0x15/0x20 fs/file_table.c:243 task_work_run+0x199/0x270 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x9bb/0x1ad0 kernel/exit.c:865 do_group_exit+0x149/0x400 kernel/exit.c:968 SYSC_exit_group kernel/exit.c:979 [inline] SyS_exit_group+0x1d/0x20 kernel/exit.c:977 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7
The buggy address belongs to the object at ffff8801bdd58180 which belongs to the cache kmalloc-2048 of size 2048 The buggy address is located 784 bytes inside of 2048-byte region [ffff8801bdd58180, ffff8801bdd58980) The buggy address belongs to the page: page:ffffea0006f75600 count:1 mapcount:0 mapping:ffff8801bdd58180 index:0x0 compound_mapcount: 0 flags: 0x2fffc0000008100(slab|head) raw: 02fffc0000008100 ffff8801bdd58180 0000000000000000 0000000100000003 raw: ffffea0007330d20 ffffea0007268aa0 ffff8801dac00c40 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff8801bdd58380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801bdd58400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801bdd58480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff8801bdd58500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801bdd58580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
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On Fri, 30 Mar 2018 01:01:01 +0200, syzbot wrote:
Hello,
syzbot hit the following crash on upstream commit 0b412605ef5f5c64b31f19e2910b1d5eba9929c3 (Thu Mar 29 01:07:23 2018 +0000) Merge tag 'drm-fixes-for-v4.16-rc8' of git://people.freedesktop.org/~airlied/linux syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=8e62ff4e07aa2ce87826
So far this crash happened 3 times on upstream. C reproducer: https://syzkaller.appspot.com/x/repro.c?id=6219387178582016 syzkaller reproducer: https://syzkaller.appspot.com/x/repro.syz?id=5176598244360192 Raw console output: https://syzkaller.appspot.com/x/log.txt?id=5815694612496384 Kernel config: https://syzkaller.appspot.com/x/.config?id=-8440362230543204781 compiler: gcc (GCC) 7.1.1 20170620
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+8e62ff4e07aa2ce87826@syzkaller.appspotmail.com It will help syzbot understand when the bug is fixed. See footer for details. If you forward the report, please keep this part and the footer.
================================================================== BUG: KASAN: use-after-free in snd_pcm_timer_resolution+0xa3/0xc0 sound/core/pcm_timer.c:72 Read of size 4 at addr ffff8801bdd58490 by task syzkaller702213/13238
CPU: 0 PID: 13238 Comm: syzkaller702213 Not tainted 4.16.0-rc7+ #370 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report+0x23c/0x360 mm/kasan/report.c:412 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432 snd_pcm_timer_resolution+0xa3/0xc0 sound/core/pcm_timer.c:72 snd_timer_resolution sound/core/timer.c:439 [inline] snd_timer_notify1+0x10f/0x400 sound/core/timer.c:462 snd_timer_start1+0x586/0x8f0 sound/core/timer.c:522 snd_timer_start+0x5d/0xa0 sound/core/timer.c:634 snd_timer_user_start.isra.12+0xde/0x130 sound/core/timer.c:1878 snd_timer_user_continue sound/core/timer.c:1902 [inline] __snd_timer_user_ioctl+0x1771/0x2c10 sound/core/timer.c:1977 snd_timer_user_ioctl+0x5f/0x7d sound/core/timer.c:1992
(snip)
So this looks like a race between ALSA PCM and ALSA timer interfaces. When a PCM timer is accessed during closing the corresponding PCM substream, it may lead to such a UAF.
The fix patch is below. I'll queue it after testing locally.
thanks,
Takashi
-- 8< -- From: Takashi Iwai tiwai@suse.de Subject: [PATCH] ALSA: pcm: Fix UAF at PCM release via PCM timer access
The PCM runtime object is created and freed dynamically at PCM stream open / close time. This is tracked via substream->runtime, and it's cleared at snd_pcm_detach_substream().
The runtime object assignment is protected by PCM open_mutex, so for all PCM operations, it's safely handled. However, each PCM substream provides also an ALSA timer interface, and user-space can access to this while closing a PCM substream. This may eventually lead to a UAF, as snd_pcm_timer_resolution() tries to access the runtime while clearing it in other side.
Fortunately, it's the only concurrent access from the PCM timer, and it merely reads runtime->timer_resolution field. So, we can avoid the race by reordering kfree() and wrapping the substream->runtime clearance with the corresponding timer lock.
Reported-by: syzbot+8e62ff4e07aa2ce87826@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/core/pcm.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/sound/core/pcm.c b/sound/core/pcm.c index 09ee8c6b9f75..66ac89aad681 100644 --- a/sound/core/pcm.c +++ b/sound/core/pcm.c @@ -28,6 +28,7 @@ #include <sound/core.h> #include <sound/minors.h> #include <sound/pcm.h> +#include <sound/timer.h> #include <sound/control.h> #include <sound/info.h>
@@ -1054,8 +1055,13 @@ void snd_pcm_detach_substream(struct snd_pcm_substream *substream) snd_free_pages((void*)runtime->control, PAGE_ALIGN(sizeof(struct snd_pcm_mmap_control))); kfree(runtime->hw_constraints.rules); - kfree(runtime); + /* Avoid concurrent access to runtime via PCM timer interface */ + if (substream->timer) + spin_lock_irq(&substream->timer->lock); substream->runtime = NULL; + if (substream->timer) + spin_unlock_irq(&substream->timer->lock); + kfree(runtime); put_pid(substream->pid); substream->pid = NULL; substream->pstr->substream_opened--;
Hi.
[This is an automated email]
This commit has been processed because it contains a -stable tag. The stable tag indicates that it's relevant for the following trees: all
The bot has also determined it's probably a bug fixing patch. (score: 98.8113)
The bot has tested the following trees: v4.15.15, v4.14.32, v4.9.92, v4.4.126,
v4.15.15: Build OK! v4.14.32: Build OK! v4.9.92: Build OK! v4.4.126: Build OK!
Please let us know if you'd like to have this patch included in a stable tree.
-- Thanks. Sasha
participants (3)
-
Sasha Levin -
syzbot -
Takashi Iwai