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

syzbot found the following crash on:

HEAD commit: 6c83d0d5 Merge branch 'for-linus-5.1-rc1' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15765b0b200000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e1aaa1cfbfe1abf
dashboard link: https://syzkaller.appspot.com/bug?extid=a39b5d3c50e55e24fb4d
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=122294a3200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a39b5d3c50e55e24fb4d@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:352 [inline]
BUG: KASAN: slab-out-of-bounds in do_convert sound/core/oss/linear.c:48
[inline]
BUG: KASAN: slab-out-of-bounds in convert sound/core/oss/linear.c:81
[inline]
BUG: KASAN: slab-out-of-bounds in linear_transfer
sound/core/oss/linear.c:110 [inline]
BUG: KASAN: slab-out-of-bounds in linear_transfer+0x6de/0x970
sound/core/oss/linear.c:88
Read of size 1 at addr ffff88809899f0b8 by task syz-executor.2/7877

CPU: 1 PID: 7877 Comm: syz-executor.2 Not tainted 5.0.0+ #24
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+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x123/0x190 mm/kasan/generic.c:191
memcpy+0x24/0x50 mm/kasan/common.c:132
memcpy include/linux/string.h:352 [inline]
do_convert sound/core/oss/linear.c:48 [inline]
convert sound/core/oss/linear.c:81 [inline]
linear_transfer sound/core/oss/linear.c:110 [inline]
linear_transfer+0x6de/0x970 sound/core/oss/linear.c:88
snd_pcm_plug_read_transfer+0x1a1/0x2f0 sound/core/oss/pcm_plugin.c:651
snd_pcm_oss_read2+0x1f0/0x3f0 sound/core/oss/pcm_oss.c:1474
snd_pcm_oss_read1 sound/core/oss/pcm_oss.c:1531 [inline]
snd_pcm_oss_read+0x53a/0x6a0 sound/core/oss/pcm_oss.c:2751
__vfs_read+0x8d/0x110 fs/read_write.c:416
vfs_read+0x194/0x3e0 fs/read_write.c:452
ksys_read+0xea/0x1f0 fs/read_write.c:578
__do_sys_read fs/read_write.c:588 [inline]
__se_sys_read fs/read_write.c:586 [inline]
__ia32_sys_read+0x71/0xb0 fs/read_write.c:586
do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
do_fast_syscall_32+0x281/0xc98 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f66869
Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90
90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f7f620cc EFLAGS: 00000296 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000200012c0
RDX: 0000000000001000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 7877:
save_stack+0x45/0xd0 mm/kasan/common.c:75
set_track mm/kasan/common.c:87 [inline]
__kasan_kmalloc mm/kasan/common.c:497 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:470
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:511
__do_kmalloc_node mm/slab.c:3686 [inline]
__kmalloc_node+0x4e/0x70 mm/slab.c:3693
kmalloc_node include/linux/slab.h:588 [inline]
kvmalloc_node+0x68/0x100 mm/util.c:430
kvmalloc include/linux/mm.h:605 [inline]
kvzalloc include/linux/mm.h:613 [inline]
snd_pcm_plugin_alloc+0x585/0x770 sound/core/oss/pcm_plugin.c:70
snd_pcm_plug_alloc+0x148/0x330 sound/core/oss/pcm_plugin.c:129
snd_pcm_oss_change_params_locked+0x2118/0x3750
sound/core/oss/pcm_oss.c:1038
snd_pcm_oss_change_params+0x7b/0xd0 sound/core/oss/pcm_oss.c:1101
snd_pcm_oss_get_active_substream+0x136/0x190 sound/core/oss/pcm_oss.c:1118
snd_pcm_oss_get_rate sound/core/oss/pcm_oss.c:1768 [inline]
snd_pcm_oss_set_rate sound/core/oss/pcm_oss.c:1760 [inline]
snd_pcm_oss_ioctl+0x8f7/0x3430 sound/core/oss/pcm_oss.c:2607
snd_pcm_oss_ioctl_compat+0x24/0x30 sound/core/oss/pcm_oss.c:2734
__do_compat_sys_ioctl fs/compat_ioctl.c:1052 [inline]
__se_compat_sys_ioctl fs/compat_ioctl.c:998 [inline]
__ia32_compat_sys_ioctl+0x197/0x620 fs/compat_ioctl.c:998
do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
do_fast_syscall_32+0x281/0xc98 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff88809899e500
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 3000 bytes inside of
4096-byte region [ffff88809899e500, ffff88809899f500)
The buggy address belongs to the page:
page:ffffea0002626780 count:1 mapcount:0 mapping:ffff88812c3f0dc0 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea00022bc088 ffffea0002841208 ffff88812c3f0dc0
raw: 0000000000000000 ffff88809899e500 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809899ef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88809899f000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff88809899f080: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc
^
ffff88809899f100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88809899f180: fc fc fc fc fc fc fc fc fc fc fc fc 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:
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