BUG: unable to handle kernel NULL pointer dereference in blk_throtl_update_limit_valid

[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.


netlink: 14 bytes leftover after parsing attributes in process
`syz-executor6'.
BUG: unable to handle kernel NULL pointer dereference at 0000000000000098
IP: blk_throtl_update_limit_valid.isra.19+0x6a/0x2e0
block/blk-throttle.c:580
PGD 213563067 P4D 213563067 PUD 214f2a067 PMD 0
Oops: 0000 [#1] SMP
Dumping ftrace buffer:
(ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 3445 Comm: kworker/1:3 Not tainted 4.15.0-rc3-next-20171214+ #67
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: events __blk_release_queue
RIP: 0010:blk_throtl_update_limit_valid.isra.19+0x6a/0x2e0
block/blk-throttle.c:580
RSP: 0018:ffffc90002e13d30 EFLAGS: 00010093
RAX: ffff8801e125c600 RBX: ffff8801df611c00 RCX: ffffffff81714e8a
RDX: 0000000000000000 RSI: 00000000d36b0597 RDI: 0000000000000086
RBP: ffffc90002e13d68 R08: 0000000000000001 R09: 000000000000000a
R10: ffffc90002e13cb8 R11: 000000000000000a R12: 0000000000000000
R13: ffff8801dfdcd808 R14: ffffffff817178f0 R15: 0000000000000098
FS: 0000000000000000(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000098 CR3: 0000000213784000 CR4: 00000000001426e0
DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
throtl_pd_offline+0x4e/0x80 block/blk-throttle.c:602
blkg_destroy+0x93/0x270 block/blk-cgroup.c:327
blkg_destroy_all+0x69/0xe0 block/blk-cgroup.c:372
blkcg_exit_queue+0x21/0x40 block/blk-cgroup.c:1202
__blk_release_queue+0x54/0x180 block/blk-sysfs.c:802
process_one_work+0x288/0x7a0 kernel/workqueue.c:2112
worker_thread+0x43/0x4d0 kernel/workqueue.c:2246
kthread+0x149/0x170 kernel/kthread.c:238
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
Code: c7 40 07 08 83 e8 c7 15 b1 ff e8 52 85 b3 ff 85 c0 59 74 12 e8 c8 54
ba ff 80 3d aa f0 a9 01 00 0f 84 fd 01 00 00 e8 b6 54 ba ff <49> 8b 07 31
ff 48 8b 80 c8 06 00 00 48 8b 70 28 e8 e1 d9 b7 ff
RIP: blk_throtl_update_limit_valid.isra.19+0x6a/0x2e0
block/blk-throttle.c:580 RSP: ffffc90002e13d30
CR2: 0000000000000098
---[ end trace b30dc449e3987ceb ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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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