syzbot


KASAN: use-after-free Read in snd_timer_resolution

Status: fixed on 2020/02/19 00:41
Reported-by: syzbot+b27e2837b883b189bbd5@syzkaller.appspotmail.com
Fix commit: 20f2e4c228c7 ALSA: seq: Fix racy access for queue timer in proc read
First crash: 1554d, last: 1554d
Fix bisection: fixed by (bisect log) :
commit 20f2e4c228c712158113583947f4e16691e951f6
Author: Takashi Iwai <tiwai@suse.de>
Date: Wed Jan 15 20:37:33 2020 +0000

  ALSA: seq: Fix racy access for queue timer in proc read

  
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in snd_timer_resolution sound C 5 1540d 1558d 15/26 fixed on 2020/02/18 14:31
linux-4.14 KASAN: use-after-free Read in snd_timer_resolution C done 1 1552d 1552d 1/1 fixed on 2020/02/21 03:21

Sample crash report:
audit: type=1400 audit(1579437284.122:36): avc:  denied  { map } for  pid=8045 comm="syz-executor234" path="/root/syz-executor234651426" dev="sda1" ino=16483 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in snd_timer_resolution+0xf1/0x110 sound/core/timer.c:467
Read of size 8 at addr ffff88808e6ff3c0 by task syz-executor234/8059

CPU: 1 PID: 8059 Comm: syz-executor234 Not tainted 4.19.97-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x197/0x210 lib/dump_stack.c:118
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:396
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 snd_timer_resolution+0xf1/0x110 sound/core/timer.c:467
 snd_seq_info_timer_read+0x95/0x2f1 sound/core/seq/seq_timer.c:489
 snd_info_seq_show+0xcb/0x120 sound/core/info.c:378
 seq_read+0x4ca/0x1110 fs/seq_file.c:229
 proc_reg_read+0x1f8/0x2b0 fs/proc/inode.c:231
 do_loop_readv_writev fs/read_write.c:701 [inline]
 do_loop_readv_writev fs/read_write.c:688 [inline]
 do_iter_read+0x490/0x640 fs/read_write.c:925
 vfs_readv+0xf0/0x160 fs/read_write.c:987
 do_preadv+0x1c4/0x280 fs/read_write.c:1071
 __do_sys_preadv fs/read_write.c:1121 [inline]
 __se_sys_preadv fs/read_write.c:1116 [inline]
 __x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1116
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4413a9
Code: e8 ac e8 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 eb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffdf921a718 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004413a9
RDX: 0000000000000227 RSI: 00000000200017c0 RDI: 0000000000000004
RBP: 00007ffdf921a730 R08: 000000000000000f R09: 00000000000000c2
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402120
R13: 00000000004021b0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 8055:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc mm/kasan/kasan.c:553 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:531
 kmem_cache_alloc_trace+0x152/0x760 mm/slab.c:3625
 kmalloc include/linux/slab.h:515 [inline]
 kzalloc include/linux/slab.h:709 [inline]
 snd_timer_instance_new+0x4f/0x3d0 sound/core/timer.c:111
 snd_timer_open+0x989/0x1850 sound/core/timer.c:321
 snd_seq_timer_open+0x240/0x580 sound/core/seq/seq_timer.c:290
 queue_use+0xcb/0x240 sound/core/seq/seq_queue.c:502
 snd_seq_queue_alloc+0x2c5/0x4d0 sound/core/seq/seq_queue.c:189
 snd_seq_ioctl_create_queue+0xb0/0x330 sound/core/seq/seq_clientmgr.c:1531
 snd_seq_kernel_client_ctl+0xf8/0x140 sound/core/seq/seq_clientmgr.c:2355
 alloc_seq_queue.isra.0+0xdc/0x180 sound/core/seq/oss/seq_oss_init.c:370
 snd_seq_oss_open+0x2ff/0x960 sound/core/seq/oss/seq_oss_init.c:228
 odev_open+0x70/0x90 sound/core/seq/oss/seq_oss.c:138
 soundcore_open+0x453/0x610 sound/sound_core.c:598
 chrdev_open+0x245/0x6b0 fs/char_dev.c:423
 do_dentry_open+0x4c3/0x1210 fs/open.c:796
 vfs_open+0xa0/0xd0 fs/open.c:905
 do_last fs/namei.c:3418 [inline]
 path_openat+0x10d7/0x45e0 fs/namei.c:3534
 do_filp_open+0x1a1/0x280 fs/namei.c:3564
 do_sys_open+0x3fe/0x550 fs/open.c:1088
 __do_sys_openat fs/open.c:1115 [inline]
 __se_sys_openat fs/open.c:1109 [inline]
 __x64_sys_openat+0x9d/0x100 fs/open.c:1109
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8055:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xcf/0x220 mm/slab.c:3822
 snd_timer_close_locked+0x7da/0xc00 sound/core/timer.c:416
 snd_timer_close+0x8e/0xf0 sound/core/timer.c:442
 snd_seq_timer_close+0x95/0xd0 sound/core/seq/seq_timer.c:329
 queue_delete+0x52/0xb0 sound/core/seq/seq_queue.c:147
 snd_seq_queue_delete+0x4e/0x70 sound/core/seq/seq_queue.c:209
 snd_seq_ioctl_delete_queue+0x6a/0x90 sound/core/seq/seq_clientmgr.c:1553
 snd_seq_kernel_client_ctl+0xf8/0x140 sound/core/seq/seq_clientmgr.c:2355
 delete_seq_queue.part.0+0xb6/0x120 sound/core/seq/oss/seq_oss_init.c:389
 delete_seq_queue sound/core/seq/oss/seq_oss_init.c:385 [inline]
 snd_seq_oss_release+0x116/0x150 sound/core/seq/oss/seq_oss_init.c:434
 odev_release+0x54/0x80 sound/core/seq/oss/seq_oss.c:153
 __fput+0x2dd/0x8b0 fs/file_table.c:278
 ____fput+0x16/0x20 fs/file_table.c:309
 task_work_run+0x145/0x1c0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0xc1f/0x30d0 kernel/exit.c:880
 do_group_exit+0x135/0x370 kernel/exit.c:983
 __do_sys_exit_group kernel/exit.c:994 [inline]
 __se_sys_exit_group kernel/exit.c:992 [inline]
 __x64_sys_exit_group+0x44/0x50 kernel/exit.c:992
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808e6ff3c0
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 0 bytes inside of
 256-byte region [ffff88808e6ff3c0, ffff88808e6ff4c0)
The buggy address belongs to the page:
page:ffffea000239bfc0 count:1 mapcount:0 mapping:ffff88812c31c7c0 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffffea00022b5a88 ffffea00023643c8 ffff88812c31c7c0
raw: 0000000000000000 ffff88808e6ff000 000000010000000c 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808e6ff280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808e6ff300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88808e6ff380: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                           ^
 ffff88808e6ff400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808e6ff480: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/01/19 12:37 linux-4.19.y dc4ba5be1bab bc8bc756 .config console log report syz C ci2-linux-4-19
2020/01/19 11:14 linux-4.19.y dc4ba5be1bab bc8bc756 .config console log report ci2-linux-4-19
* Struck through repros no longer work on HEAD.