Re: [PATCH for-6.6/block] blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before init

[Jens Axboe]

On Wed, 16 Aug 2023 09:56:23 -1000, Tejun Heo wrote:
> blk-iocost sometimes causes the following crash:
> 
>   BUG: kernel NULL pointer dereference, address: 00000000000000e0
>   ...
>   RIP: 0010:_raw_spin_lock+0x17/0x30
>   Code: be 01 02 00 00 e8 79 38 39 ff 31 d2 89 d0 5d c3 0f 1f 00 0f 1f 44 00 00 55 48 89 e5 65 ff 05 48 d0 34 7e b9 01 00 00 00 31 c0 <f0> 0f b1 0f 75 02 5d c3 89 c6 e8 ea 04 00 00 5d c3 0f 1f 84 00 00
>   RSP: 0018:ffffc900023b3d40 EFLAGS: 00010046
>   RAX: 0000000000000000 RBX: 00000000000000e0 RCX: 0000000000000001
>   RDX: ffffc900023b3d20 RSI: ffffc900023b3cf0 RDI: 00000000000000e0
>   RBP: ffffc900023b3d40 R08: ffffc900023b3c10 R09: 0000000000000003
>   R10: 0000000000000064 R11: 000000000000000a R12: ffff888102337000
>   R13: fffffffffffffff2 R14: ffff88810af408c8 R15: ffff8881070c3600
>   FS:  00007faaaf364fc0(0000) GS:ffff88842fdc0000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 00000000000000e0 CR3: 00000001097b1000 CR4: 0000000000350ea0
>   Call Trace:
>    <TASK>
>    ioc_weight_write+0x13d/0x410
>    cgroup_file_write+0x7a/0x130
>    kernfs_fop_write_iter+0xf5/0x170
>    vfs_write+0x298/0x370
>    ksys_write+0x5f/0xb0
>    __x64_sys_write+0x1b/0x20
>    do_syscall_64+0x3d/0x80
>    entry_SYSCALL_64_after_hwframe+0x46/0xb0
> 
> [...]

Applied, thanks!

[1/1] blk-cgroup: Fix NULL deref caused by blkg_policy_data being installed before init
      commit: ec14a87ee1999b19d8b7ed0fa95fea80644624ae

Best regards,
-- 
Jens Axboe