KASAN: null-ptr-deref Write in linear_transfer

[syzbot]

Hello,

syzkaller hit the following crash on
30a7acd573899fd8b8ac39236eff6468b195ac7d
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


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Reported-by: syzbot+a8f564...@syzkaller.appspotmail.com
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==================================================================
BUG: KASAN: null-ptr-deref in memcpy include/linux/string.h:344 [inline]
BUG: KASAN: null-ptr-deref in do_convert sound/core/oss/linear.c:52 [inline]
BUG: KASAN: null-ptr-deref in convert sound/core/oss/linear.c:81 [inline]
BUG: KASAN: null-ptr-deref in linear_transfer+0x634/0x900
sound/core/oss/linear.c:110
Write of size 2 at addr (null) by task syzkaller360172/7860

CPU: 0 PID: 7860 Comm: syzkaller360172 Not tainted 4.15.0-rc6+ #155
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+0x194/0x257 lib/dump_stack.c:53
kasan_report_error mm/kasan/report.c:349 [inline]
kasan_report+0x13b/0x340 mm/kasan/report.c:409
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
memcpy+0x37/0x50 mm/kasan/kasan.c:303
memcpy include/linux/string.h:344 [inline]
do_convert sound/core/oss/linear.c:52 [inline]
convert sound/core/oss/linear.c:81 [inline]
linear_transfer+0x634/0x900 sound/core/oss/linear.c:110
snd_pcm_plug_write_transfer+0x22d/0x420 sound/core/oss/pcm_plugin.c:611
snd_pcm_oss_write2+0x260/0x420 sound/core/oss/pcm_oss.c:1311
snd_pcm_oss_sync1+0x1cc/0x550 sound/core/oss/pcm_oss.c:1530
snd_pcm_oss_sync+0x5b6/0x830 sound/core/oss/pcm_oss.c:1604
snd_pcm_oss_release+0x20b/0x280 sound/core/oss/pcm_oss.c:2431
__fput+0x327/0x7e0 fs/file_table.c:210
____fput+0x15/0x20 fs/file_table.c:244
task_work_run+0x199/0x270 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x9bb/0x1ad0 kernel/exit.c:865
do_group_exit+0x149/0x400 kernel/exit.c:968
get_signal+0x73f/0x16c0 kernel/signal.c:2335
do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath arch/x86/entry/common.c:264 [inline]
do_syscall_32_irqs_on arch/x86/entry/common.c:333 [inline]
do_fast_syscall_32+0xbfd/0xf9d arch/x86/entry/common.c:389
entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7fcac79
RSP: 002b:00000000f7f8412c EFLAGS: 00000292 ORIG_RAX: 00000000000000f0
RAX: fffffffffffffe00 RBX: 00000000080fd024 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000080fd024
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
==================================================================
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 7860 Comm: syzkaller360172 Tainted: G B
4.15.0-rc6+ #155
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+0x194/0x257 lib/dump_stack.c:53
panic+0x1e4/0x41c kernel/panic.c:183
kasan_end_report+0x50/0x50 mm/kasan/report.c:176
kasan_report_error mm/kasan/report.c:356 [inline]
kasan_report+0x144/0x340 mm/kasan/report.c:409
check_memory_region_inline mm/kasan/kasan.c:260 [inline]
check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
memcpy+0x37/0x50 mm/kasan/kasan.c:303
memcpy include/linux/string.h:344 [inline]
do_convert sound/core/oss/linear.c:52 [inline]
convert sound/core/oss/linear.c:81 [inline]
linear_transfer+0x634/0x900 sound/core/oss/linear.c:110
snd_pcm_plug_write_transfer+0x22d/0x420 sound/core/oss/pcm_plugin.c:611
snd_pcm_oss_write2+0x260/0x420 sound/core/oss/pcm_oss.c:1311
snd_pcm_oss_sync1+0x1cc/0x550 sound/core/oss/pcm_oss.c:1530
snd_pcm_oss_sync+0x5b6/0x830 sound/core/oss/pcm_oss.c:1604
snd_pcm_oss_release+0x20b/0x280 sound/core/oss/pcm_oss.c:2431
__fput+0x327/0x7e0 fs/file_table.c:210
____fput+0x15/0x20 fs/file_table.c:244
task_work_run+0x199/0x270 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x9bb/0x1ad0 kernel/exit.c:865
do_group_exit+0x149/0x400 kernel/exit.c:968
get_signal+0x73f/0x16c0 kernel/signal.c:2335
do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath arch/x86/entry/common.c:264 [inline]
do_syscall_32_irqs_on arch/x86/entry/common.c:333 [inline]
do_fast_syscall_32+0xbfd/0xf9d arch/x86/entry/common.c:389
entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7fcac79
RSP: 002b:00000000f7f8412c EFLAGS: 00000292 ORIG_RAX: 00000000000000f0
RAX: fffffffffffffe00 RBX: 00000000080fd024 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000080fd024
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[Eric Biggers]

Still reproducible even after all the fixes currently in sound/for-linus.

Eric

[Takashi Iwai]

Interesting, I can't reproduce it on my VM any longer...


Takashi

[Eric Biggers]

No longer occurring, last occurrence was Mar 29 on commit a2601d78b77aa.
Seems to have been fixed by commit 02a5d6925cd3:

#syz fix: ALSA: pcm: Avoid potential races between OSS ioctls and read/write

The reproducer was opening /dev/dsp1, then concurrently writing to it and
calling the SNDCTL_DSP_SPEED ioctl.

- Eric

[Takashi Iwai]

Good to hear. Yes, this should have been covered by the change.
Thanks for checking!


Takashi