Re: KASAN: use-after-free Read in snd_timer_process_callbacks

From: syzbot
Date: Wed Apr 10 2019 - 01:47:14 EST

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In reply to: syzbot: "KASAN: use-after-free Read in snd_timer_process_callbacks"
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syzbot has found a reproducer for the following crash on:

HEAD commit: cfd24a53 Add linux-next specific files for 20190409
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=111d56af200000
kernel config: https://syzkaller.appspot.com/x/.config?x=75160b904dadd291
dashboard link: https://syzkaller.appspot.com/bug?extid=58813d77154713f4de15
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=137ba6af200000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1749585b200000

The bug was bisected to:

commit a7588c896b05444929ecb3d0115481988720abf6
Author: Takashi Iwai <tiwai@xxxxxxx>
Date: Wed Mar 27 15:56:08 2019 +0000

ALSA: timer: Check ack_list emptiness instead of bit flag

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1100d3ab200000
final crash: https://syzkaller.appspot.com/x/report.txt?x=1300d3ab200000
console output: https://syzkaller.appspot.com/x/log.txt?x=1500d3ab200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+58813d77154713f4de15@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: a7588c896b05 ("ALSA: timer: Check ack_list emptiness instead of bit flag")

==================================================================
BUG: KASAN: use-after-free in __list_del_entry_valid+0xd2/0xf5 lib/list_debug.c:42
Read of size 8 at addr ffff8880a9363ee0 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.1.0-rc4-next-20190409 #21
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
__list_del_entry_valid+0xd2/0xf5 lib/list_debug.c:42
__list_del_entry include/linux/list.h:117 [inline]
list_del_init include/linux/list.h:176 [inline]
snd_timer_process_callbacks+0x7f/0x2f0 sound/core/timer.c:763
snd_timer_interrupt sound/core/timer.c:883 [inline]
snd_timer_interrupt+0x578/0xdd0 sound/core/timer.c:804
snd_hrtimer_callback+0x219/0x3e0 sound/core/hrtimer.c:64
__run_hrtimer kernel/time/hrtimer.c:1389 [inline]
__hrtimer_run_queues+0x33e/0xde0 kernel/time/hrtimer.c:1451
hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1509
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1035 [inline]
smp_apic_timer_interrupt+0x120/0x570 arch/x86/kernel/apic/apic.c:1060
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
</IRQ>
RIP: 0010:native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:58
Code: ff ff ff 48 89 c7 48 89 45 d8 e8 99 65 8e fa 48 8b 45 d8 e9 ce fe ff ff 48 89 df e8 88 65 8e fa eb 82 90 90 90 90 90 90 fb f4 <c3> 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 f4 c3 90 90 90 90 90 90
RSP: 0018:ffffffff88807d08 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff1124ad9 RBX: ffffffff8887a100 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000006 RDI: ffffffff8887a97c
RBP: ffffffff88807d38 R08: ffffffff8887a100 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff889256b8 R14: 0000000000000000 R15: 0000000000000000
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:567
default_idle_call+0x36/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x386/0x570 kernel/sched/idle.c:262
cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353
rest_init+0x245/0x37b init/main.c:450
arch_call_rest_init+0xe/0x1b
start_kernel+0x816/0x84f init/main.c:747
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

Allocated by task 7722:
save_stack+0x45/0xd0 mm/kasan/common.c:75
set_track mm/kasan/common.c:87 [inline]
__kasan_kmalloc mm/kasan/common.c:497 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:470
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:511
kmem_cache_alloc_trace+0x151/0x760 mm/slab.c:3621
kmalloc include/linux/slab.h:547 [inline]
kzalloc include/linux/slab.h:742 [inline]
snd_timer_instance_new+0x4f/0x3d0 sound/core/timer.c:109
snd_timer_open+0x8a7/0x1760 sound/core/timer.c:313
snd_seq_timer_open+0x240/0x590 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:1522
snd_seq_ioctl+0x224/0x3e0 sound/core/seq/seq_clientmgr.c:2138
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xd6e/0x1390 fs/ioctl.c:696
ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7722:
save_stack+0x45/0xd0 mm/kasan/common.c:75
set_track mm/kasan/common.c:87 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:459
kasan_slab_free+0xe/0x10 mm/kasan/common.c:467
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3821
snd_timer_close_locked+0x6fd/0xd60 sound/core/timer.c:405
snd_timer_close+0x2e/0x70 sound/core/timer.c:430
snd_seq_timer_close+0x91/0xd0 sound/core/seq/seq_timer.c:329
queue_delete+0x52/0xb0 sound/core/seq/seq_queue.c:147
snd_seq_queue_client_leave+0x36/0x170 sound/core/seq/seq_queue.c:584
seq_free_client1.part.0+0xf3/0x270 sound/core/seq/seq_clientmgr.c:263
seq_free_client1 sound/core/seq/seq_clientmgr.c:256 [inline]
seq_free_client+0x80/0xf0 sound/core/seq/seq_clientmgr.c:285
snd_seq_release+0x55/0xf0 sound/core/seq/seq_clientmgr.c:366
__fput+0x2e5/0x8d0 fs/file_table.c:278
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x14a/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop+0x273/0x2c0 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880a9363e40
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 160 bytes inside of
256-byte region [ffff8880a9363e40, ffff8880a9363f40)
The buggy address belongs to the page:
page:ffffea0002a4d8c0 count:1 mapcount:0 mapping:ffff88812c3f07c0 index:0xffff8880a9363940
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002a21a48 ffffea0002a2e048 ffff88812c3f07c0
raw: ffff8880a9363940 ffff8880a9363080 0000000100000009 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a9363d80: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
ffff8880a9363e00: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb

ffff8880a9363e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

^
ffff8880a9363f00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880a9363f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Next message: Michael Ellerman: "Re: [PATCH RFC 1/5] cpu/speculation: Add 'cpu_spec_mitigations=' cmdline options"
Previous message: Naga Sureshkumar Relli: "RE: linux-next: Tree for Apr 9 (spi/spi-zynq-qspi.c)"
In reply to: syzbot: "KASAN: use-after-free Read in snd_timer_process_callbacks"
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