WARNING in do_dentry_open

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 68abbe729567 Merge branch 'akpm' (patches from Andrew)
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=130146af800000
kernel config: https://syzkaller.appspot.com/x/.config?x=e5a4673d4582131c
dashboard link: https://syzkaller.appspot.com/bug?extid=2e7fcab0f56fdbb330b8
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1591756f800000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=152236af800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2e7fca...@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
WARNING: CPU: 1 PID: 4508 at fs/open.c:778 do_dentry_open+0x4ad/0xe40
fs/open.c:778
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 4508 Comm: syz-executor867 Not tainted 4.17.0+ #90
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+0x1b9/0x294 lib/dump_stack.c:113
panic+0x22f/0x4de kernel/panic.c:184
__warn.cold.8+0x163/0x1b3 kernel/panic.c:536
report_bug+0x252/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:do_dentry_open+0x4ad/0xe40 fs/open.c:778
Code: 7b 28 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00
0f 85 15 08 00 00 48 c7 43 28 00 00 00 00 e8 f3 6d ba ff <0f> 0b e8 ec 6d
ba ff 48 8d 43 18 41 be ed ff ff ff 48 89 45 c0 e9
RSP: 0018:ffff8801afcaf7c8 EFLAGS: 00010293
RAX: ffff8801afe08400 RBX: ffff8801b099e0c0 RCX: ffffffff81bfccf6
RDX: 0000000000000000 RSI: ffffffff81bfcf6d RDI: ffff8801b099e0e8
RBP: ffff8801afcaf840 R08: ffff8801afe08400 R09: ffffed0036aa2afc
R10: ffffed0036aa2afc R11: ffff8801b55157e3 R12: ffff8801ab28d4b0
R13: ffff8801ab28d6a8 R14: 0000000000000000 R15: ffff8801b099e13c
vfs_open+0x139/0x230 fs/open.c:908
do_last fs/namei.c:3370 [inline]
path_openat+0x1717/0x4dc0 fs/namei.c:3511
do_filp_open+0x249/0x350 fs/namei.c:3545
do_sys_open+0x56f/0x740 fs/open.c:1101
__do_sys_openat fs/open.c:1128 [inline]
__se_sys_openat fs/open.c:1122 [inline]
__x64_sys_openat+0x9d/0x100 fs/open.c:1122
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x43ff09
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 6b 45 00 00 c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe4eafe4f8 EFLAGS: 00000217 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 2f30656c69662f2e RCX: 000000000043ff09
RDX: 0000000000000040 RSI: 0000000020000100 RDI: ffffffffffffff9c
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000004 R11: 0000000000000217 R12: 0000000000401830
R13: 00000000004018c0 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
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[Dmitry Vyukov]

On Fri, Jun 8, 2018 at 3:11 PM, syzbot
<syzbot+2e7fca...@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 68abbe729567 Merge branch 'akpm' (patches from Andrew)
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=130146af800000
> kernel config: https://syzkaller.appspot.com/x/.config?x=e5a4673d4582131c
> dashboard link: https://syzkaller.appspot.com/bug?extid=2e7fcab0f56fdbb330b8
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1591756f800000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=152236af800000

Looking at the reproducer this seems to be related to bpf.
+bpf maintainers

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[Daniel Borkmann]

On 06/08/2018 03:34 PM, Dmitry Vyukov wrote:
> On Fri, Jun 8, 2018 at 3:11 PM, syzbot
> <syzbot+2e7fca...@syzkaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit: 68abbe729567 Merge branch 'akpm' (patches from Andrew)
>> git tree: upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=130146af800000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=e5a4673d4582131c
>> dashboard link: https://syzkaller.appspot.com/bug?extid=2e7fcab0f56fdbb330b8
>> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1591756f800000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=152236af800000
>
> Looking at the reproducer this seems to be related to bpf.
> +bpf maintainers

Indeed, thanks! Already working on a fix right now.

[Daniel Borkmann]

#syz fix: bpf: implement dummy fops for bpf objects