Hello,

syzbot found the following crash on:

HEAD commit: 6980b7f6 Add linux-next specific files for 20191111 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=16a82b9ae00000 kernel config: https://syzkaller.appspot.com/x/.config?x=2af7db1972ec750e dashboard link: https://syzkaller.appspot.com/bug?extid=4a89123a06517944d4c1 compiler: gcc (GCC) 9.0.0 20181231 (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+4a89123a06517944d4c1@syzkaller.appspotmail.com

================================================================== BUG: KASAN: use-after-free in snd_timer_close_locked+0xb5f/0xbd0 sound/core/timer.c:380 Read of size 8 at addr ffff8880a906be78 by task syz-executor.4/9580

CPU: 1 PID: 9580 Comm: syz-executor.4 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 snd_timer_close_locked+0xb5f/0xbd0 sound/core/timer.c:380 snd_timer_close+0x88/0xf0 sound/core/timer.c:418 snd_seq_timer_close+0x91/0xe0 sound/core/seq/seq_timer.c:318 queue_delete+0x52/0xb0 sound/core/seq/seq_queue.c:134 snd_seq_queue_delete+0x4e/0x70 sound/core/seq/seq_queue.c:196 snd_seq_ioctl_delete_queue+0x6a/0x90 sound/core/seq/seq_clientmgr.c:1570 snd_seq_kernel_client_ctl+0xf8/0x140 sound/core/seq/seq_clientmgr.c:2353 delete_seq_queue.part.0+0xb6/0x120 sound/core/seq/oss/seq_oss_init.c:376 delete_seq_queue sound/core/seq/oss/seq_oss_init.c:372 [inline] snd_seq_oss_release+0x116/0x150 sound/core/seq/oss/seq_oss_init.c:421 odev_release+0x54/0x80 sound/core/seq/oss/seq_oss.c:140 __fput+0x2ff/0x890 fs/file_table.c:280 ____fput+0x16/0x20 fs/file_table.c:313 task_work_run+0x145/0x1c0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:163 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] syscall_return_slowpath arch/x86/entry/common.c:274 [inline] do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x413db1 Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 RSP: 002b:00007fffcff8b860 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000413db1 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004 RBP: 0000000000000001 R08: 00000000ca6eb3e2 R09: 00000000ca6eb3e6 R10: 00007fffcff8b940 R11: 0000000000000293 R12: 000000000075bf20 R13: 00000000000361f0 R14: 00000000007607e0 R15: 000000000075bf2c

Allocated by task 9581: 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 9581: 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 ffff8880a906be00 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 120 bytes inside of 256-byte region [ffff8880a906be00, ffff8880a906bf00) The buggy address belongs to the page: page:ffffea0002a41ac0 refcount:1 mapcount:0 mapping:ffff8880aa4008c0 index:0x0 flags: 0x1fffc0000000200(slab) raw: 01fffc0000000200 ffffea00025db908 ffff8880aa401648 ffff8880aa4008c0 raw: 0000000000000000 ffff8880a906b000 0000000100000008 0000000000000000 page dumped because: kasan: bad access detected

Memory state around the buggy address: ffff8880a906bd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8880a906bd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

ffff8880a906be00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

^ ffff8880a906be80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880a906bf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ==================================================================

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