On Fri, Jan 19, 2018 at 01:58:01PM -0800, syzbot wrote:

Hello,

syzbot hit the following crash on mmots commit 2164355612187e55e8d60a28d2cc6b2337841a7e (Fri Jan 19 01:07:54 2018 +0000) pci: test for unexpectedly disabled bridges

So far this crash happened 2 times on mmots. 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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BUG: unable to handle kernel paging request at ffffc90001691000 IP: memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:65 PGD 1dad2c067 P4D 1dad2c067 PUD 1dad2d067 PMD 1c6a8f067 PTE 0 Oops: 0002 [#1] SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 5739 Comm: syzkaller592073 Not tainted 4.15.0-rc8-mm1+ #57 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:65 RSP: 0018:ffff8801cbbdfb78 EFLAGS: 00010246 RAX: fffff520002d3f00 RBX: ffffc90001691000 RCX: 000000000000ee51 RDX: 000000000000ee51 RSI: 0000000000000000 RDI: ffffc90001691000 RBP: ffff8801cbbdfb98 R08: fffff520002d3fcb R09: ffffc90001691000 R10: 0000000000001dcb R11: fffff520002d3fca R12: 000000000000ee51 R13: 0000000000000000 R14: 00007ffffffff000 R15: 000000002001be51 FS: 00007f88ae7d7700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffc90001691000 CR3: 00000001ccefa005 CR4: 00000000001606e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: memset include/linux/string.h:329 [inline] _copy_from_user+0xe9/0x110 lib/usercopy.c:16 copy_from_user include/linux/uaccess.h:147 [inline] snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1347 [inline] snd_pcm_oss_write+0x438/0x880 sound/core/oss/pcm_oss.c:2659 __vfs_write+0xef/0x970 fs/read_write.c:480 vfs_write+0x189/0x510 fs/read_write.c:544 SYSC_write fs/read_write.c:589 [inline] SyS_write+0xef/0x220 fs/read_write.c:581 entry_SYSCALL_64_fastpath+0x29/0xa0 RIP: 0033:0x44a559 RSP: 002b:00007f88ae7d6da8 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00000000006dcc24 RCX: 000000000044a559 RDX: 000000000000fe51 RSI: 000000002000c000 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000293 R12: 00000000006dcc20 R13: 7073642f7665642f R14: 00800000c0045006 R15: 0000000000000001 Code: 48 c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 <f3> aa 4c 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 RIP: memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:65 RSP: ffff8801cbbdfb78 CR2: ffffc90001691000 ---[ end trace 8f421641f3e10f44 ]--- Kernel panic - not syncing: Fatal exception Dumping ftrace buffer: (ftrace buffer empty) Kernel Offset: disabled Rebooting in 86400 seconds..

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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.

syzbot will keep track of this bug report. If you forgot to add the Reported-by tag, once the fix for this bug is merged into any tree, please reply to this email with: #syz fix: exact-commit-title

The reproducer is unreliable, but this is another one that seems to have been fixed by commit 02a5d6925cd34:

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

The reproducer is opening /dev/dsp1, then concurrently doing write() and ioctl(SNDCTL_DSP_CHANNELS).

- Eric