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SubjectKASAN: slab-out-of-bounds Read in default_write_copy_kernel
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Hello,

syzbot found the following crash on:

HEAD commit: 7c98a4261827 Merge tag 'ceph-for-4.20-rc4' of https://gith..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=142c8893400000
kernel config: https://syzkaller.appspot.com/x/.config?x=73e2bc0cb6463446
dashboard link: https://syzkaller.appspot.com/bug?extid=d4503ae45b65c5bc1194
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1789354d400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=162ebe2b400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d4503ae45b65c5bc1194@syzkaller.appspotmail.com

RDX: 0000000056da83a0 RSI: 00000000200000c0 RDI: 0000000000000004
RBP: 00000000006cf018 R08: 0000000000000001 R09: 0000000000000037
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:352 [inline]
BUG: KASAN: slab-out-of-bounds in default_write_copy_kernel+0xe1/0x140
sound/core/pcm_lib.c:1946
Read of size 64 at addr ffff8881cee03c40 by task syz-executor636/6021

CPU: 1 PID: 6021 Comm: syz-executor636 Not tainted 4.20.0-rc3+ #347
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+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
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
memcpy+0x23/0x50 mm/kasan/kasan.c:302
memcpy include/linux/string.h:352 [inline]
default_write_copy_kernel+0xe1/0x140 sound/core/pcm_lib.c:1946
interleaved_copy+0xd1/0x110 sound/core/pcm_lib.c:2007
__snd_pcm_lib_xfer+0x115f/0x1f23 sound/core/pcm_lib.c:2227
snd_pcm_oss_write3+0xe9/0x220 sound/core/oss/pcm_oss.c:1237
io_playback_transfer+0x27d/0x310 sound/core/oss/io.c:47
snd_pcm_plug_write_transfer+0x374/0x490 sound/core/oss/pcm_plugin.c:620
snd_pcm_oss_write2+0x25d/0x450 sound/core/oss/pcm_oss.c:1366
snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1432 [inline]
snd_pcm_oss_write+0x567/0xa60 sound/core/oss/pcm_oss.c:2775
__vfs_write+0x119/0x9f0 fs/read_write.c:485
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x444119
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 d8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffdf4510538 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000444119
RDX: 0000000056da83a0 RSI: 00000000200000c0 RDI: 0000000000000004
RBP: 00000000006cf018 R08: 0000000000000001 R09: 0000000000000037
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6021:
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
__do_kmalloc_node mm/slab.c:3684 [inline]
__kmalloc_node+0x50/0x70 mm/slab.c:3691
kmalloc_node include/linux/slab.h:589 [inline]
kvmalloc_node+0x65/0xf0 mm/util.c:416
kvmalloc include/linux/mm.h:577 [inline]
kvzalloc include/linux/mm.h:585 [inline]
snd_pcm_plugin_alloc+0x577/0x770 sound/core/oss/pcm_plugin.c:70
snd_pcm_plug_alloc+0x218/0x340 sound/core/oss/pcm_plugin.c:117
snd_pcm_oss_change_params_locked+0x2209/0x3c60
sound/core/oss/pcm_oss.c:1038
snd_pcm_oss_make_ready_locked+0xbc/0x130 sound/core/oss/pcm_oss.c:1183
snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1397 [inline]
snd_pcm_oss_write+0x51e/0xa60 sound/core/oss/pcm_oss.c:2775
__vfs_write+0x119/0x9f0 fs/read_write.c:485
vfs_write+0x1fc/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2446:
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:3817
blk_mq_hw_sysfs_release+0x42/0x60 block/blk-mq-sysfs.c:25
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put.cold.9+0x287/0x2e4 lib/kobject.c:708
blk_mq_release+0xf2/0x210 block/blk-mq.c:2478
__blk_release_queue+0x228/0x510 block/blk-sysfs.c:862
process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
kthread+0x35a/0x440 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff8881cee03c40
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
32-byte region [ffff8881cee03c40, ffff8881cee03c60)
The buggy address belongs to the page:
page:ffffea00073b80c0 count:1 mapcount:0 mapping:ffff8881da8001c0
index:0xffff8881cee03fc1
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea0007433308 ffff8881da801248 ffff8881da8001c0
raw: ffff8881cee03fc1 ffff8881cee03000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881cee03b00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8881cee03b80: fb fb fb fb fc fc fc fc 00 fc fc fc fc fc fc fc
> ffff8881cee03c00: fb fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
^
ffff8881cee03c80: 00 00 fc fc fc fc fc fc fb fb fb fb fc fc fc fc
ffff8881cee03d00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

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syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

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