KASAN: use-after-free Read in delete_and_unsubscribe_port (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 7cc2a8ea Merge tag 'block-5.8-2020-07-01' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11561e7b100000
kernel config: https://syzkaller.appspot.com/x/.config?x=7be693511b29b338
dashboard link: https://syzkaller.appspot.com/bug?extid=1a54a94bd32716796edd
compiler: gcc (GCC) 10.1.0-syz 20200507
userspace arch: i386

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1a54a9...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in list_empty include/linux/list.h:282 [inline]
BUG: KASAN: use-after-free in delete_and_unsubscribe_port+0x420/0x4f0 sound/core/seq/seq_ports.c:530
Read of size 8 at addr ffff88809533de50 by task syz-executor.0/29034

CPU: 0 PID: 29034 Comm: syz-executor.0 Not tainted 5.8.0-rc3-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+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
list_empty include/linux/list.h:282 [inline]
delete_and_unsubscribe_port+0x420/0x4f0 sound/core/seq/seq_ports.c:530
snd_seq_port_disconnect+0x433/0x5c0 sound/core/seq/seq_ports.c:610
snd_seq_ioctl_unsubscribe_port+0x1fc/0x400 sound/core/seq/seq_clientmgr.c:1525
snd_seq_ioctl+0x202/0x3e0 sound/core/seq/seq_clientmgr.c:2157
snd_seq_ioctl_compat+0xdc/0x2d0 sound/core/seq/seq_compat.c:109
__do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:847
do_syscall_32_irqs_on+0x3f/0x60 arch/x86/entry/common.c:403
__do_fast_syscall_32 arch/x86/entry/common.c:448 [inline]
do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:474
entry_SYSENTER_compat+0x6d/0x7c arch/x86/entry/entry_64_compat.S:138
RIP: 0023:0xf7ff0569
Code: Bad RIP value.
RSP: 002b:00000000f5deb0cc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000040505331
RDX: 0000000020000200 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 29030:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
kmem_cache_alloc_trace+0x14f/0x2d0 mm/slab.c:3551
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
snd_seq_port_connect+0x5d/0x520 sound/core/seq/seq_ports.c:553
snd_seq_ioctl_subscribe_port+0x1fc/0x400 sound/core/seq/seq_clientmgr.c:1484
snd_seq_ioctl+0x202/0x3e0 sound/core/seq/seq_clientmgr.c:2157
snd_seq_ioctl_compat+0xdc/0x2d0 sound/core/seq/seq_compat.c:109
__do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:847
do_syscall_32_irqs_on+0x3f/0x60 arch/x86/entry/common.c:403
__do_fast_syscall_32 arch/x86/entry/common.c:448 [inline]
do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:474
entry_SYSENTER_compat+0x6d/0x7c arch/x86/entry/entry_64_compat.S:138

Freed by task 29035:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]
__kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x103/0x2c0 mm/slab.c:3757
snd_seq_port_disconnect+0x4c1/0x5c0 sound/core/seq/seq_ports.c:614
snd_seq_ioctl_unsubscribe_port+0x1fc/0x400 sound/core/seq/seq_clientmgr.c:1525
snd_seq_ioctl+0x202/0x3e0 sound/core/seq/seq_clientmgr.c:2157
snd_seq_ioctl_compat+0xdc/0x2d0 sound/core/seq/seq_compat.c:109
__do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:847
do_syscall_32_irqs_on+0x3f/0x60 arch/x86/entry/common.c:403
__do_fast_syscall_32 arch/x86/entry/common.c:448 [inline]
do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:474
entry_SYSENTER_compat+0x6d/0x7c arch/x86/entry/entry_64_compat.S:138

The buggy address belongs to the object at ffff88809533de00
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 80 bytes inside of
128-byte region [ffff88809533de00, ffff88809533de80)
The buggy address belongs to the page:
page:ffffea000254cf40 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88809533d100
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00029c2e48 ffffea0002257d48 ffff8880aa000700
raw: ffff88809533d100 ffff88809533d000 000000010000000a 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809533dd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809533dd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88809533de00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88809533de80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88809533df00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: d3590ebf Merge tag 'audit-pr-20200729' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1207e0b8900000
kernel config: https://syzkaller.appspot.com/x/.config?x=812bbfcb6ae2cd60
dashboard link: https://syzkaller.appspot.com/bug?extid=1a54a94bd32716796edd
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11b227f8900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+1a54a9...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in list_empty include/linux/list.h:282 [inline]

BUG: KASAN: use-after-free in delete_and_unsubscribe_port+0x8b/0x450 sound/core/seq/seq_ports.c:530
Read of size 8 at addr ffff888098523060 by task syz-executor.0/7202

CPU: 1 PID: 7202 Comm: syz-executor.0 Not tainted 5.8.0-rc7-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+0x1f0/0x31e lib/dump_stack.c:118
print_address_description+0x66/0x5a0 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report+0x132/0x1d0 mm/kasan/report.c:530
list_empty include/linux/list.h:282 [inline]
delete_and_unsubscribe_port+0x8b/0x450 sound/core/seq/seq_ports.c:530
snd_seq_port_disconnect+0x568/0x610 sound/core/seq/seq_ports.c:612
snd_seq_ioctl_unsubscribe_port+0x349/0x6c0 sound/core/seq/seq_clientmgr.c:1525
snd_seq_oss_midi_close+0x397/0x620 sound/core/seq/oss/seq_oss_midi.c:405
snd_seq_oss_synth_reset+0x335/0x8b0 sound/core/seq/oss/seq_oss_synth.c:406
snd_seq_oss_reset+0x5b/0x250 sound/core/seq/oss/seq_oss_init.c:435
snd_seq_oss_ioctl+0x5c2/0x1090 sound/core/seq/oss/seq_oss_ioctl.c:93
odev_ioctl+0x51/0x70 sound/core/seq/oss/seq_oss.c:174
vfs_ioctl fs/ioctl.c:48 [inline]
ksys_ioctl fs/ioctl.c:753 [inline]
__do_sys_ioctl fs/ioctl.c:762 [inline]
__se_sys_ioctl+0xf9/0x160 fs/ioctl.c:760
do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45c429
Code: 8d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6e48930c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000000154c0 RCX: 000000000045c429
RDX: 0000000000000000 RSI: 0000000000005100 RDI: 0000000000000003
RBP: 000000000078bf38 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007ffe51b9d10f R14: 00007f6e489319c0 R15: 000000000078bf0c

Allocated by task 7202:
save_stack mm/kasan/common.c:48 [inline]
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc+0x103/0x140 mm/kasan/common.c:494
kmem_cache_alloc_trace+0x234/0x300 mm/slab.c:3551

kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]

snd_seq_port_connect+0x66/0x460 sound/core/seq/seq_ports.c:553
snd_seq_ioctl_subscribe_port+0x349/0x6c0 sound/core/seq/seq_clientmgr.c:1484
snd_seq_oss_midi_open+0x4db/0x830 sound/core/seq/oss/seq_oss_midi.c:364
snd_seq_oss_synth_setup_midi+0x108/0x510 sound/core/seq/oss/seq_oss_synth.c:269
snd_seq_oss_open+0x899/0xe90 sound/core/seq/oss/seq_oss_init.c:261
odev_open+0x5e/0x90 sound/core/seq/oss/seq_oss.c:125
chrdev_open+0x498/0x580 fs/char_dev.c:414
do_dentry_open+0x813/0x1070 fs/open.c:828
do_open fs/namei.c:3243 [inline]
path_openat+0x278d/0x37f0 fs/namei.c:3360
do_filp_open+0x191/0x3a0 fs/namei.c:3387
do_sys_openat2+0x463/0x770 fs/open.c:1179
do_sys_open fs/open.c:1195 [inline]
__do_sys_openat fs/open.c:1209 [inline]
__se_sys_openat fs/open.c:1204 [inline]
__x64_sys_openat+0x1c8/0x1f0 fs/open.c:1204
do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 7203:
save_stack mm/kasan/common.c:48 [inline]

set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]

__kasan_slab_free+0x114/0x170 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x10a/0x220 mm/slab.c:3757
snd_seq_port_disconnect+0x570/0x610 sound/core/seq/seq_ports.c:614
snd_seq_ioctl_unsubscribe_port+0x349/0x6c0 sound/core/seq/seq_clientmgr.c:1525
snd_seq_oss_midi_close+0x397/0x620 sound/core/seq/oss/seq_oss_midi.c:405
snd_seq_oss_synth_reset+0x335/0x8b0 sound/core/seq/oss/seq_oss_synth.c:406
snd_seq_oss_reset+0x5b/0x250 sound/core/seq/oss/seq_oss_init.c:435
snd_seq_oss_ioctl+0x5c2/0x1090 sound/core/seq/oss/seq_oss_ioctl.c:93
odev_ioctl+0x51/0x70 sound/core/seq/oss/seq_oss.c:174
vfs_ioctl fs/ioctl.c:48 [inline]
ksys_ioctl fs/ioctl.c:753 [inline]
__do_sys_ioctl fs/ioctl.c:762 [inline]
__se_sys_ioctl+0xf9/0x160 fs/ioctl.c:760
do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888098523000

which belongs to the cache kmalloc-128 of size 128

The buggy address is located 96 bytes inside of
128-byte region [ffff888098523000, ffff888098523080)

The buggy address belongs to the page:

page:ffffea00026148c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002613988 ffffea000262c648 ffff8880aa400700
raw: 0000000000000000 ffff888098523000 0000000100000010 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff888098522f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888098522f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888098523000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888098523080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888098523100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

[Zhang, Qiang]

________________________________________
发件人: linux-ker...@vger.kernel.org <linux-ker...@vger.kernel.org> 代表 syzbot <syzbot+1a54a9...@syzkaller.appspotmail.com>
发送时间: 2020年7月30日 11:33
收件人: alsa-dev...@alsa-project.org; alsa-...@alsa-project.org; linux-...@vger.kernel.org; pe...@perex.cz; syzkall...@googlegroups.com; ti...@suse.com
主题: Re: KASAN: use-after-free Read in delete_and_unsubscribe_port (2)

syzbot has found a reproducer for the following issue on:

HEAD commit: d3590ebf Merge tag 'audit-pr-20200729' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1207e0b8900000
kernel config: https://syzkaller.appspot.com/x/.config?x=812bbfcb6ae2cd60
dashboard link: https://syzkaller.appspot.com/bug?extid=1a54a94bd32716796edd
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11b227f8900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1a54a9...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in list_empty include/linux/list.h:282 [inline]
BUG: KASAN: use-after-free in delete_and_unsubscribe_port+0x8b/0x450 sound/core/seq/seq_ports.c:530
Read of size 8 at addr ffff888098523060 by task syz-executor.0/7202

CPU: 1 PID: 7202 Comm: syz-executor.0 Not tainted 5.8.0-rc7-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+0x1f0/0x31e lib/dump_stack.c:118
print_address_description+0x66/0x5a0 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report+0x132/0x1d0 mm/kasan/report.c:530
list_empty include/linux/list.h:282 [inline]

It 's looks likely "subs->ref_count" problem.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+1a54a9...@syzkaller.appspotmail.com

Tested on:

commit: 644a76b2 ALSA: seq: oss: Serialize ioctls
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git test/seq-oss-serialize
kernel config: https://syzkaller.appspot.com/x/.config?x=f76bdcf4905eb7c9

dashboard link: https://syzkaller.appspot.com/bug?extid=1a54a94bd32716796edd
compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

Note: testing is done by a robot and is best-effort only.