[alsa-devel] KASAN: use-after-free Read in snd_seq_timer_interrupt

syzbot syzbot+d5136d4d3240cbe45a2a at syzkaller.appspotmail.com
Wed Oct 24 16:11:02 CEST 2018 

Hello,

syzbot found the following crash on:

HEAD commit:    44786880df19 Merge branch 'parisc-4.20-1' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=178c8bad400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5071a2e3cb82c943
dashboard link: https://syzkaller.appspot.com/bug?extid=d5136d4d3240cbe45a2a
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

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+d5136d4d3240cbe45a2a at syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in snd_seq_timer_interrupt+0x364/0x3e0  
sound/core/seq/seq_timer.c:145
Read of size 8 at addr ffff8801cf71c118 by task syz-executor0/24085

CPU: 1 PID: 24085 Comm: syz-executor0 Not tainted 4.19.0+ #300
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+0x244/0x39d lib/dump_stack.c:113
  print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  snd_seq_timer_interrupt+0x364/0x3e0 sound/core/seq/seq_timer.c:145
  snd_timer_interrupt+0x9ff/0x1660 sound/core/timer.c:855
  snd_timer_s_function+0xcd/0x130 sound/core/timer.c:1094
  call_timer_fn+0x272/0x920 kernel/time/timer.c:1326
  expire_timers kernel/time/timer.c:1363 [inline]
  __run_timers+0x7e5/0xc70 kernel/time/timer.c:1682
  run_timer_softirq+0x52/0xb0 kernel/time/timer.c:1695
  __do_softirq+0x308/0xb7e kernel/softirq.c:292
  invoke_softirq kernel/softirq.c:373 [inline]
  irq_exit+0x17f/0x1c0 kernel/softirq.c:413
  exiting_irq arch/x86/include/asm/apic.h:536 [inline]
  smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:801
  </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:761  
[inline]
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160  
[inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xaf/0xd0  
kernel/locking/spinlock.c:184
Code: 30 f6 31 89 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c  
02 00 75 28 48 83 3d 28 cd 7c 01 00 74 15 48 89 df 57 9d <0f> 1f 44 00 00  
eb ad e8 7c 52 4b f9 eb bb 0f 0b 0f 0b e8 8a 54 0e
RSP: 0018:ffff880181eaf508 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 0000000000000282 RCX: 0000000000000000
RDX: 1ffffffff1263ec6 RSI: 0000000000000001 RDI: 0000000000000282
RBP: ffff880181eaf518 R08: ffff88018378a140 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801c0b94ac0
R13: ffff8801c0b94300 R14: ffff8801daf2cc40 R15: 0000000000000001
  try_to_wake_up+0x10a/0x12e0 kernel/sched/core.c:2056
  wake_up_process kernel/sched/core.c:2124 [inline]
  wake_up_q+0xa4/0x100 kernel/sched/core.c:440
  futex_wake+0x61f/0x760 kernel/futex.c:1556
  do_futex+0x2e4/0x26d0 kernel/futex.c:3533
  __do_sys_futex kernel/futex.c:3589 [inline]
  __se_sys_futex kernel/futex.c:3557 [inline]
  __x64_sys_futex+0x472/0x6a0 kernel/futex.c:3557
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:0000000000a3fbf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: ffffffffffffffda RBX: 000000000072bfa0 RCX: 0000000000457569
RDX: 0000000000000000 RSI: 0000000000000081 RDI: 000000000072bfa8
RBP: 00000000000003b7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000a3fcb0 R11: 0000000000000246 R12: 000000000072bfac
R13: 000000000072bfac R14: 0000000000000003 R15: 0000000000000001

Allocated by task 24073:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
  kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
  kmalloc include/linux/slab.h:513 [inline]
  kzalloc include/linux/slab.h:707 [inline]
  queue_new sound/core/seq/seq_queue.c:113 [inline]
  snd_seq_queue_alloc+0xab/0x5b0 sound/core/seq/seq_queue.c:185
  snd_seq_ioctl_create_queue+0xb0/0x320 sound/core/seq/seq_clientmgr.c:1522
  snd_seq_ioctl+0x253/0x440 sound/core/seq/seq_clientmgr.c:2138
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:501 [inline]
  do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
  __do_sys_ioctl fs/ioctl.c:709 [inline]
  __se_sys_ioctl fs/ioctl.c:707 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 24072:
  save_stack+0x43/0xd0 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:3498 [inline]
  kfree+0xcf/0x230 mm/slab.c:3813
  queue_delete+0x90/0xb0 sound/core/seq/seq_queue.c:156
  snd_seq_queue_client_leave+0x36/0x170 sound/core/seq/seq_queue.c:584
  seq_free_client1.part.9+0xf4/0x270 sound/core/seq/seq_clientmgr.c:263
  seq_free_client1 sound/core/seq/seq_clientmgr.c:256 [inline]
  seq_free_client+0x82/0x100 sound/core/seq/seq_clientmgr.c:285
  snd_seq_release+0x51/0xe0 sound/core/seq/seq_clientmgr.c:366
  __fput+0x385/0xa30 fs/file_table.c:278
  ____fput+0x15/0x20 fs/file_table.c:309
  task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:193 [inline]
  exit_to_usermode_loop+0x318/0x380 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+0x6be/0x820 arch/x86/entry/common.c:293
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801cf71c0c0
  which belongs to the cache kmalloc-512 of size 512
The buggy address is located 88 bytes inside of
  512-byte region [ffff8801cf71c0c0, ffff8801cf71c2c0)
The buggy address belongs to the page:
page:ffffea00073dc700 count:1 mapcount:0 mapping:ffff8801da800940 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea00073a4fc8 ffffea000761f4c8 ffff8801da800940
raw: 0000000000000000 ffff8801cf71c0c0 0000000100000006 0000000000000000
kobject: 'loop5' (00000000172d3417): kobject_uevent_env
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801cf71c000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801cf71c080: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> ffff8801cf71c100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                             ^
  ffff8801cf71c180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801cf71c200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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