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BUG: KASAN: use-after-free in __list_add_valid+0x9a/0xa0 lib/list_debug.c:26
Read of size 8 at addr ffff888095ac8078 by task syz-executor.0/4457

CPU: 1 PID: 4457 Comm: syz-executor.0 Not tainted 5.4.0-rc6-next-20191111 #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.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:634
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 __list_add_valid+0x9a/0xa0 lib/list_debug.c:26
 __list_add include/linux/list.h:60 [inline]
 list_add_tail include/linux/list.h:93 [inline]
 list_move_tail include/linux/list.h:214 [inline]
 check_matching_master_slave.part.0+0x116/0x550 sound/core/timer.c:179
 check_matching_master_slave sound/core/timer.c:177 [inline]
 snd_timer_check_slave sound/core/timer.c:207 [inline]
 snd_timer_open+0x466/0x1150 sound/core/timer.c:270
 snd_timer_user_tselect sound/core/timer.c:1738 [inline]
 __snd_timer_user_ioctl.isra.0+0x7ed/0x2070 sound/core/timer.c:2008
 snd_timer_user_ioctl+0x7a/0xa7 sound/core/timer.c:2038
 vfs_ioctl fs/ioctl.c:47 [inline]
 file_ioctl fs/ioctl.c:545 [inline]
 do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
 __do_sys_ioctl fs/ioctl.c:756 [inline]
 __se_sys_ioctl fs/ioctl.c:754 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a219
Code: ad 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f41e77d2c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a219
RDX: 0000000020029fcc RSI: 0000000040345410 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f41e77d36d4
R13: 00000000004cf428 R14: 00000000004d9760 R15: 00000000ffffffff

Allocated by task 4339:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc mm/kasan/common.c:510 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
 kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3551
 kmalloc include/linux/slab.h:556 [inline]
 kzalloc include/linux/slab.h:670 [inline]
 snd_timer_instance_new+0x4a/0x300 sound/core/timer.c:96
 snd_timer_user_tselect sound/core/timer.c:1725 [inline]
 __snd_timer_user_ioctl.isra.0+0x665/0x2070 sound/core/timer.c:2008
 snd_timer_user_ioctl+0x7a/0xa7 sound/core/timer.c:2038
 vfs_ioctl fs/ioctl.c:47 [inline]
 file_ioctl fs/ioctl.c:545 [inline]
 do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
 __do_sys_ioctl fs/ioctl.c:756 [inline]
 __se_sys_ioctl fs/ioctl.c:754 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4339:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 kasan_set_free_info mm/kasan/common.c:332 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3757
 snd_timer_instance_free sound/core/timer.c:120 [inline]
 snd_timer_instance_free+0x7c/0xa0 sound/core/timer.c:114
 snd_timer_user_tselect sound/core/timer.c:1740 [inline]
 __snd_timer_user_ioctl.isra.0+0x160d/0x2070 sound/core/timer.c:2008
 snd_timer_user_ioctl+0x7a/0xa7 sound/core/timer.c:2038
 vfs_ioctl fs/ioctl.c:47 [inline]
 file_ioctl fs/ioctl.c:545 [inline]
 do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:749
 __do_sys_ioctl fs/ioctl.c:756 [inline]
 __se_sys_ioctl fs/ioctl.c:754 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888095ac8000
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 120 bytes inside of
 256-byte region [ffff888095ac8000, ffff888095ac8100)
The buggy address belongs to the page:
page:ffffea000256b200 refcount:1 mapcount:0 mapping:ffff8880aa4008c0 index:0xffff888095ac8c00
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0001815608 ffffea0001eb9308 ffff8880aa4008c0
raw: ffff888095ac8c00 ffff888095ac8000 0000000100000005 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888095ac7f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888095ac7f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888095ac8000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff888095ac8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888095ac8100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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