Hello,

syzbot hit the following crash on upstream commit 1b88accf6a659c46d5c8e68912896f112bf882bb (Thu Mar 8 01:49:33 2018 +0000) Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

So far this crash happened 3 times on upstream. C reproducer is attached. syzkaller reproducer is attached. Raw console output is attached. compiler: gcc (GCC) 7.1.1 20170620 .config is attached.

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IPVS: ftp: loaded support on port[0] = 21 audit: type=1400 audit(1520612143.836:8): avc: denied { map } for pid=4259 comm="syzkaller191035" path="/dev/dsp1" dev="devtmpfs" ino=1250 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:sound_device_t:s0 tclass=chr_file permissive=1 IPVS: ftp: loaded support on port[0] = 21 IPVS: ftp: loaded support on port[0] = 21 ================================================================== BUG: KASAN: use-after-free in snd_mask_test include/sound/pcm_params.h:141 [inline] BUG: KASAN: use-after-free in snd_pcm_oss_get_formats+0x320/0x380 sound/core/oss/pcm_oss.c:1770 Read of size 4 at addr ffff8801bace4024 by task syzkaller191035/4271

CPU: 0 PID: 4271 Comm: syzkaller191035 Not tainted 4.16.0-rc4+ #346 IPVS: ftp: loaded support on port[0] = 21 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 IPVS: ftp: loaded support on port[0] = 21 print_address_description+0x73/0x250 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report+0x23c/0x360 mm/kasan/report.c:412 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432 snd_mask_test include/sound/pcm_params.h:141 [inline] snd_pcm_oss_get_formats+0x320/0x380 sound/core/oss/pcm_oss.c:1770 snd_pcm_oss_set_format sound/core/oss/pcm_oss.c:1784 [inline] snd_pcm_oss_ioctl+0x1e2f/0x39f0 sound/core/oss/pcm_oss.c:2515 IPVS: ftp: loaded support on port[0] = 21 IPVS: ftp: loaded support on port[0] = 21 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x4499e9 RSP: 002b:00007fa1872a5da8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000006dbc24 RCX: 00000000004499e9 RDX: 0000000020000080 RSI: 00800000c0045005 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc20 R13: 7073642f7665642f R14: 00800000c0045005 R15: 0000000000000003

Allocated by task 4271: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552 kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3607 kmalloc include/linux/slab.h:512 [inline] snd_pcm_oss_get_formats+0x1c7/0x380 sound/core/oss/pcm_oss.c:1760 snd_pcm_oss_set_format sound/core/oss/pcm_oss.c:1784 [inline] snd_pcm_oss_ioctl+0x1e2f/0x39f0 sound/core/oss/pcm_oss.c:2515 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 4271: save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527 __cache_free mm/slab.c:3485 [inline] kfree+0xd9/0x260 mm/slab.c:3800 snd_pcm_oss_get_formats+0x216/0x380 sound/core/oss/pcm_oss.c:1766 snd_pcm_oss_set_format sound/core/oss/pcm_oss.c:1784 [inline] snd_pcm_oss_ioctl+0x1e2f/0x39f0 sound/core/oss/pcm_oss.c:2515 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686 SYSC_ioctl fs/ioctl.c:701 [inline] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801bace4000 which belongs to the cache kmalloc-1024 of size 1024 The buggy address is located 36 bytes inside of 1024-byte region [ffff8801bace4000, ffff8801bace4400) The buggy address belongs to the page: page:ffffea0006eb3900 count:1 mapcount:0 mapping:ffff8801bace4000 index:0x0 compound_mapcount: 0 flags: 0x2fffc0000008100(slab|head) raw: 02fffc0000008100 ffff8801bace4000 0000000000000000 0000000100000007 raw: ffffea000761d7a0 ffffea0006eb39a0 ffff8801dac00ac0 0000000000000000 page dumped because: kasan: bad access detected

Memory state around the buggy address: ffff8801bace3f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8801bace3f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

ffff8801bace4000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

^ ffff8801bace4080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801bace4100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================

--- This bug is generated by a dumb bot. It may contain errors. See https://goo.gl/tpsmEJ for details. Direct all questions to syzkaller@googlegroups.com.

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