KASAN: use-after-free Write in snd_rawmidi_kernel_write1

Status: fixed on 2020/06/15 08:02
Fix commit: a507658fdb2a ALSA: rawmidi: Fix racy buffer resize under concurrent accesses
First crash: 1464d, last: 1434d
Fix bisection: fixed by (bisect log) :
commit a507658fdb2ad8ca282b0eb42f2a40b805deb1e6
Author: Takashi Iwai <>
Date: Thu May 7 11:44:56 2020 +0000

  ALSA: rawmidi: Fix racy buffer resize under concurrent accesses

Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Write in snd_rawmidi_kernel_write1 sound 1 683d 681d 0/26 auto-obsoleted due to no activity on 2022/10/03 20:00
linux-4.14 KASAN: use-after-free Write in snd_rawmidi_kernel_write1 1 1465d 1465d 0/1 auto-closed as invalid on 2020/08/12 12:40
Fix bisection attempts (2)
Created Duration User Patch Repo Result
2020/06/14 13:54 3h53m bisect fix linux-4.19.y job log (1)
2020/05/15 13:12 41m bisect fix linux-4.19.y job log (0) log

Sample crash report:
BUG: KASAN: use-after-free in _copy_from_user+0xef/0x140 lib/usercopy.c:12
Write of size 32 at addr ffff8880a534b3a0 by task syz-executor745/6430

CPU: 1 PID: 6430 Comm: syz-executor745 Not tainted 4.19.115-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+0x188/0x20d lib/dump_stack.c:118
 print_address_description.cold+0x7c/0x212 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+0x88/0x2b9 mm/kasan/report.c:396
 _copy_from_user+0xef/0x140 lib/usercopy.c:12
 copy_from_user include/linux/uaccess.h:147 [inline]
 snd_rawmidi_kernel_write1+0x301/0x6c0 sound/core/rawmidi.c:1282
 snd_rawmidi_write+0x2e4/0xb50 sound/core/rawmidi.c:1348
 __vfs_write+0xf7/0x760 fs/read_write.c:485
 vfs_write+0x206/0x550 fs/read_write.c:549
 ksys_write+0x12b/0x2a0 fs/read_write.c:599
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
RIP: 0033:0x44a3f9
Code: e8 5c b3 02 00 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 2b cc fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f571e99bdb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 000000000044a3f9
RDX: 0000000020000339 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
R13: 00007fff8662259f R14: 00007f571e99c9c0 R15: 20c49ba5e353f7cf

Allocated by task 6430:
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc mm/kasan/kasan.c:553 [inline]
 kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:531
 __do_kmalloc_node mm/slab.c:3689 [inline]
 __kmalloc_node+0x4c/0x70 mm/slab.c:3696
 kmalloc_node include/linux/slab.h:557 [inline]
 kvmalloc_node+0x61/0xf0 mm/util.c:423
 kvmalloc include/linux/mm.h:577 [inline]
 kvzalloc include/linux/mm.h:585 [inline]
 snd_rawmidi_runtime_create sound/core/rawmidi.c:133 [inline]
 open_substream+0x332/0x800 sound/core/rawmidi.c:277
 rawmidi_open_priv+0x58e/0x6e0 sound/core/rawmidi.c:328
 snd_rawmidi_open+0x449/0xaf0 sound/core/rawmidi.c:425
 snd_open+0x212/0x3e2 sound/core/sound.c:175
 chrdev_open+0x219/0x5c0 fs/char_dev.c:423
 do_dentry_open+0x4a8/0x1160 fs/open.c:796
 do_last fs/namei.c:3421 [inline]
 path_openat+0x1031/0x4200 fs/namei.c:3537
 do_filp_open+0x1a1/0x280 fs/namei.c:3567
 do_sys_open+0x3c0/0x500 fs/open.c:1085
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293

Freed by task 6431:
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/kasan.c:521
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xce/0x220 mm/slab.c:3822
 kvfree+0x59/0x60 mm/util.c:452
 resize_runtime_buffer+0x29e/0x370 sound/core/rawmidi.c:669
 snd_rawmidi_output_params+0x128/0x170 sound/core/rawmidi.c:682
 snd_rawmidi_ioctl+0x640/0x740 sound/core/rawmidi.c:759
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcda/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293

The buggy address belongs to the object at ffff8880a534a640
 which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 3424 bytes inside of
 4096-byte region [ffff8880a534a640, ffff8880a534b640)
The buggy address belongs to the page:
page:ffffea000294d280 count:1 mapcount:0 mapping:ffff88812c3dcdc0 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea0002942988 ffffea0002920208 ffff88812c3dcdc0
raw: 0000000000000000 ffff8880a534a640 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a534b280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a534b300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a534b380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a534b400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a534b480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/04/15 12:19 linux-4.19.y 6dd0e32665e5 3f3c5574 .config console log report syz C ci2-linux-4-19
* Struck through repros no longer work on HEAD.