KASAN: slab-out-of-bounds Read in linear_transfer (3)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1416a90ee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b
dashboard link: https://syzkaller.appspot.com/bug?extid=f153bde47a62e0b05f83
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10fe9e41e00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1522042ae00000

The bug was bisected to:

commit 65766ee0bf7fe8b3be80e2e1c3ef54ad59b29476
Author: Takashi Iwai <ti...@suse.de>
Date: Fri Nov 9 10:59:45 2018 +0000

ALSA: oss: Use kvzalloc() for local buffer allocations

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1727742ae00000
final crash: https://syzkaller.appspot.com/x/report.txt?x=14a7742ae00000
console output: https://syzkaller.appspot.com/x/log.txt?x=10a7742ae00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f153bd...@syzkaller.appspotmail.com
Fixes: 65766ee0bf7f ("ALSA: oss: Use kvzalloc() for local buffer
allocations")

==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:380 [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 ffff8880a3eb5540 by task syz-executor567/8984

CPU: 0 PID: 8984 Comm: syz-executor567 Not tainted 5.4.0-syzkaller #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:638
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
memcpy+0x24/0x50 mm/kasan/common.c:124
memcpy include/linux/string.h:380 [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+0x197/0x2e0 sound/core/oss/pcm_plugin.c:651
snd_pcm_oss_read2+0x1f0/0x3f0 sound/core/oss/pcm_oss.c:1460
snd_pcm_oss_read1 sound/core/oss/pcm_oss.c:1517 [inline]
snd_pcm_oss_read+0x548/0x6a0 sound/core/oss/pcm_oss.c:2741
__vfs_read+0x8a/0x110 fs/read_write.c:425
vfs_read+0x1f0/0x440 fs/read_write.c:461
ksys_read+0x14f/0x290 fs/read_write.c:587
__do_sys_read fs/read_write.c:597 [inline]
__se_sys_read fs/read_write.c:595 [inline]
__x64_sys_read+0x73/0xb0 fs/read_write.c:595
do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445a99
Code: e8 dc bd 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 cb 11 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f2955880ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00000000006dbc28 RCX: 0000000000445a99
RDX: 0000000000001000 RSI: 0000000020000380 RDI: 0000000000000003
RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc2c
R13: 00007ffd9643eb4f R14: 00007f29558819c0 R15: 20c49ba5e353f7cf

Allocated by task 8984:
save_stack+0x23/0x90 mm/kasan/common.c:71
set_track mm/kasan/common.c:79 [inline]
__kasan_kmalloc mm/kasan/common.c:512 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:485
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:526
__do_kmalloc_node mm/slab.c:3616 [inline]
__kmalloc_node+0x4e/0x70 mm/slab.c:3623
kmalloc_node include/linux/slab.h:579 [inline]
kvmalloc_node+0x68/0x100 mm/util.c:574
kvmalloc include/linux/mm.h:655 [inline]
kvzalloc include/linux/mm.h:663 [inline]
snd_pcm_plugin_alloc+0x585/0x770 sound/core/oss/pcm_plugin.c:70
snd_pcm_plug_alloc+0x146/0x330 sound/core/oss/pcm_plugin.c:129
snd_pcm_oss_change_params_locked+0x210f/0x3750
sound/core/oss/pcm_oss.c:1024
snd_pcm_oss_change_params+0x7b/0xd0 sound/core/oss/pcm_oss.c:1087
snd_pcm_oss_get_active_substream+0x136/0x190 sound/core/oss/pcm_oss.c:1104
snd_pcm_oss_get_rate sound/core/oss/pcm_oss.c:1754 [inline]
snd_pcm_oss_set_rate sound/core/oss/pcm_oss.c:1746 [inline]
snd_pcm_oss_ioctl+0x1794/0x33a0 sound/core/oss/pcm_oss.c:2593
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/0x790 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8880a3eb5500
which belongs to the cache kmalloc-64 of size 64
The buggy address is located 0 bytes to the right of
64-byte region [ffff8880a3eb5500, ffff8880a3eb5540)
The buggy address belongs to the page:
page:ffffea00028fad40 refcount:1 mapcount:0 mapping:ffff8880aa400380
index:0x0
raw: 00fffe0000000200 ffffea00027da7c8 ffff8880aa401348 ffff8880aa400380
raw: 0000000000000000 ffff8880a3eb5000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a3eb5400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a3eb5480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8880a3eb5500: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
^
ffff8880a3eb5580: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
ffff8880a3eb5600: 00 00 00 00 00 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.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Takashi Iwai]

On Wed, 04 Dec 2019 09:25:09 +0100,
syzbot wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 76bb8b05 Merge tag 'kbuild-v5.5' of git://git.kernel.org/p..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1416a90ee00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=dd226651cb0f364b
> dashboard link: https://syzkaller.appspot.com/bug?extid=f153bde47a62e0b05f83
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10fe9e41e00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1522042ae00000
>
> The bug was bisected to:
>
> commit 65766ee0bf7fe8b3be80e2e1c3ef54ad59b29476
> Author: Takashi Iwai <ti...@suse.de>
> Date: Fri Nov 9 10:59:45 2018 +0000
>
> ALSA: oss: Use kvzalloc() for local buffer allocations

FYI, this bisection result is bogus; before this commit, the buffer
was allocated via vmalloc and KASAN check was skipped. Now with
kvmalloc(), it goes with kmalloc which has a proper check, and the
problem surfaced since this commit.

The real culprit is a potential buffer overflow in the OSS plugin
chain. I submitted the fix patch now.


Takashi