BUG: unable to handle kernel NULL pointer dereference in free_pipe_info

[syzbot]

Hello,

syzkaller hit the following crash on
6084b576dca2e898f5c101baef151f7bfdbb606d
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.

Unfortunately, I don't have any reproducer for this bug yet.


BUG: unable to handle kernel NULL pointer dereference at 000000000000002f
IP: pipe_buf_release include/linux/pipe_fs_i.h:136 [inline]
IP: free_pipe_info+0x75/0xd0 fs/pipe.c:674
PGD 1e069b067 P4D 1e069b067 PUD 1e0d7f067 PMD 0
Oops: 0000 [#1] SMP
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 11658 Comm: syz-executor4 Not tainted 4.15.0-rc3-next-20171214+
#67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:pipe_buf_release include/linux/pipe_fs_i.h:136 [inline]
RIP: 0010:free_pipe_info+0x75/0xd0 fs/pipe.c:674
RSP: 0018:ffffc90000e27ba8 EFLAGS: 00010293
RAX: ffff8801dfa7e500 RBX: ffff8801dac70200 RCX: ffffffff81414817
RDX: 0000000000000000 RSI: ffff8802156b6800 RDI: ffff8801dac70200
RBP: ffffc90000e27bc8 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8802156b6800 R14: 000000000000001f R15: ffff880213d99820
FS: 00007f81f5ada700(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000000002f CR3: 00000001e05cc000 CR4: 00000000001426e0
Call Trace:
put_pipe_info+0x65/0x80 fs/pipe.c:561
pipe_release+0xda/0x110 fs/pipe.c:582
__fput+0x120/0x270 fs/file_table.c:209
____fput+0x15/0x20 fs/file_table.c:243
task_work_run+0xa3/0xe0 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x3e6/0x1050 kernel/exit.c:869
do_group_exit+0x60/0x100 kernel/exit.c:972
get_signal+0x36c/0xad0 kernel/signal.c:2337
do_signal+0x23/0x670 arch/x86/kernel/signal.c:809
exit_to_usermode_loop+0x13c/0x160 arch/x86/entry/common.c:161
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath+0x1b4/0x1e0 arch/x86/entry/common.c:264
entry_SYSCALL_64_fastpath+0x94/0x96
RIP: 0033:0x452a39
RSP: 002b:00007f81f5ad9ce8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000007581b8 RCX: 0000000000452a39
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000007581b8
RBP: 00000000007581b8 R08: 000000000000001a R09: 0000000000758190
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000a6f7ff R14: 00007f81f5ada9c0 R15: 000000000000000e
Code: 48 8d 14 80 48 8b 83 08 01 00 00 4c 8d 2c d0 4d 8b 75 10 4d 85 f6 74
17 e8 29 5b ea ff 49 c7 45 10 00 00 00 00 4c 89 ee 48 89 df <41> ff 56 10
e8 12 5b ea ff 41 83 c4 01 44 39 a3 d0 00 00 00 77
RIP: pipe_buf_release include/linux/pipe_fs_i.h:136 [inline] RSP:
ffffc90000e27ba8
RIP: free_pipe_info+0x75/0xd0 fs/pipe.c:674 RSP: ffffc90000e27ba8
CR2: 000000000000002f
---[ end trace 7ae396f579301f25 ]---


---
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[Eric Biggers]

Invalidating this bug since it hasn't been seen again, and it was reported while
KASAN was accidentally disabled in the syzbot kconfig due to a change to the
kconfig menus in linux-next (so this crash was possibly caused by slab
corruption elsewhere).

#syz invalid

[Goldwyn Rodrigues]

This crash looks similar to the ones discussed in
https://lkml.org/lkml/2017/10/30/780

If this can be reproduced, please share how.


--
Goldwyn

[Eric Biggers]

Hi Goldwyn,

syzkaller wasn't able to generate a reproducer for this. If it had it would
have been provided in the report.

Thanks,

- Eric