BUG: unable to handle kernel NULL pointer dereference in irq_bypass_register_consumer

[syzbot]

Hello,

syzkaller hit the following crash on
41d8c16909ebda40f7b4982a7f5e2ad102705ade
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.

syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
IP: irq_bypass_register_consumer+0xbe/0x200 virt/lib/irqbypass.c:198
PGD 20d26c067 P4D 20d26c067 PUD 20d26f067 PMD 0
Oops: 0000 [#1] SMP
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 8627 Comm: syz-executor7 Not tainted 4.15.0-rc3-next-20171213+
#66
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:irq_bypass_register_consumer+0xbe/0x200 virt/lib/irqbypass.c:198
RSP: 0018:ffffc9000691fd50 EFLAGS: 00010293
RAX: ffff88021431e2c0 RBX: 0000000000000000 RCX: ffffffff825a774e
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000691fd70 R08: ffffffff825a7710 R09: 0000000000000004
R10: ffffc9000691fd40 R11: 0000000000000004 R12: ffff88020d3d5368
R13: ffff88020ef7c980 R14: ffff88020eef2768 R15: ffff88020d370000
FS: 00007f2d09cf8700(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000010 CR3: 00000002143f1000 CR4: 00000000001426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
kvm_irqfd+0x6d4/0x860 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
kvm_vm_ioctl+0x3e2/0x9f0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3000
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0xaf/0x840 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x452a39
RSP: 002b:00007f2d09cf7c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 0000000000452a39
RDX: 0000000020080fe0 RSI: 000000004020ae76 RDI: 0000000000000003
RBP: 0000000000000562 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f61d0
R13: 00000000ffffffff R14: 00007f2d09cf86d4 R15: 0000000000000000
Code: d1 fe 4d 8b 6c 24 10 4d 39 6e 10 74 2f 4d 39 f4 74 2a 4c 89 f3 e8 33
2c d1 fe 48 8b 1b 48 81 fb 60 e1 19 83 74 43 e8 22 2c d1 fe <4c> 39 6b 10
0f 94 c2 49 39 dc 0f 94 c0 08 c2 74 d9 e8 0c 2c d1
RIP: irq_bypass_register_consumer+0xbe/0x200 virt/lib/irqbypass.c:198 RSP:
ffffc9000691fd50
CR2: 0000000000000010
---[ end trace 28b4667ba051ea9a ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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[Wanpeng Li]

2017-12-17 17:56 GMT+08:00 syzbot
<bot+dcff49641d63583853...@syzkaller.appspotmail.com>:

> Hello,
>
> syzkaller hit the following crash on
> 41d8c16909ebda40f7b4982a7f5e2ad102705ade
> 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.
>
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>

I will have a look.

Regards,
Wanpeng Li

[Eric Biggers]

syzbot is no longer reporting this crash. It seems it was reported during the
time that KASAN was accidentally disabled in the syzbot config due to a change
to the kconfig menus in linux-next. So it's probably the same as this one
(which is still happening):

#syz dup: KASAN: use-after-free Write in irq_bypass_register_consumer