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BUG: KASAN: use-after-free in snd_timer_check_master sound/core/timer.c:228 [inline]
BUG: KASAN: use-after-free in snd_timer_open+0x100a/0x1150 sound/core/timer.c:326
Read of size 8 at addr ffff888096b6da78 by task syz-executor.4/26140

CPU: 1 PID: 26140 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_check_master sound/core/timer.c:228 [inline]
 snd_timer_open+0x100a/0x1150 sound/core/timer.c:326
 snd_seq_timer_open+0x27f/0x590 sound/core/seq/seq_timer.c:281
 queue_use+0xf1/0x270 sound/core/seq/seq_queue.c:489
 snd_seq_queue_alloc+0x2c5/0x4d0 sound/core/seq/seq_queue.c:176
 snd_seq_ioctl_create_queue+0xb0/0x330 sound/core/seq/seq_clientmgr.c:1548
 snd_seq_kernel_client_ctl+0xf8/0x140 sound/core/seq/seq_clientmgr.c:2353
 alloc_seq_queue.isra.0+0xdc/0x180 sound/core/seq/oss/seq_oss_init.c:357
 snd_seq_oss_open+0x2ff/0x960 sound/core/seq/oss/seq_oss_init.c:215
 odev_open+0x70/0x90 sound/core/seq/oss/seq_oss.c:125
 soundcore_open+0x453/0x610 sound/sound_core.c:593
 chrdev_open+0x245/0x6b0 fs/char_dev.c:414
 do_dentry_open+0x4e6/0x1380 fs/open.c:797
 vfs_open+0xa0/0xd0 fs/open.c:914
 do_last fs/namei.c:3412 [inline]
 path_openat+0x10e4/0x4710 fs/namei.c:3529
 do_filp_open+0x1a1/0x280 fs/namei.c:3559
 do_sys_open+0x3fe/0x5d0 fs/open.c:1097
 __do_sys_openat fs/open.c:1124 [inline]
 __se_sys_openat fs/open.c:1118 [inline]
 __x64_sys_openat+0x9d/0x100 fs/open.c:1118
 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:00007f28ab1dcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045a219
RDX: 0000000000040100 RSI: 00000000200000c0 RDI: ffffffffffffff9c
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f28ab1dd6d4
R13: 00000000004c735b R14: 00000000004dcfa0 R15: 00000000ffffffff

Allocated by task 24605:
 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]
 alloc_fs_context+0x5a/0x780 fs/fs_context.c:261
 fs_context_for_mount+0x25/0x30 fs/fs_context.c:307
 do_new_mount fs/namespace.c:2807 [inline]
 do_mount+0x11b2/0x1b50 fs/namespace.c:3142
 ksys_mount+0xdb/0x150 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3362
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 24605:
 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
 put_fs_context+0x448/0x560 fs/fs_context.c:510
 do_new_mount fs/namespace.c:2826 [inline]
 do_mount+0x6dc/0x1b50 fs/namespace.c:3142
 ksys_mount+0xdb/0x150 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3362
 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 ffff888096b6da00
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 120 bytes inside of
 256-byte region [ffff888096b6da00, ffff888096b6db00)
The buggy address belongs to the page:
page:ffffea00025adb40 refcount:1 mapcount:0 mapping:ffff8880aa4008c0 index:0xffff888096b6de00
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea000250fec8 ffffea0002879148 ffff8880aa4008c0
raw: ffff888096b6de00 ffff888096b6d000 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888096b6d900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888096b6d980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888096b6da00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff888096b6da80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888096b6db00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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