linux-kernel - Re: [PATCH v2] firmware: dmi-sysfs: Fix null-ptr-deref in dmi_sysfs_register

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Date:   Fri, 11 Nov 2022 14:21:35 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     <linux-kernel@...r.kernel.org>, <linmq006@...il.com>
Subject: Re: [PATCH v2] firmware: dmi-sysfs: Fix null-ptr-deref in
 dmi_sysfs_register_handle

Hi,

On 2022/11/11 14:18, Greg KH wrote:
> On Fri, Nov 11, 2022 at 09:53:26AM +0800, Chen Zhongjin wrote:
>> KASAN reported a null-ptr-deref error:
>>
>> KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
>> CPU: 0 PID: 1373 Comm: modprobe
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
>> RIP: 0010:dmi_sysfs_entry_release
>> ...
>> Call Trace:
>>   <TASK>
>>   kobject_put
>>   dmi_sysfs_register_handle (drivers/firmware/dmi-sysfs.c:540) dmi_sysfs
>>   dmi_decode_table (drivers/firmware/dmi_scan.c:133)
>>   dmi_walk (drivers/firmware/dmi_scan.c:1115)
>>   dmi_sysfs_init (drivers/firmware/dmi-sysfs.c:149) dmi_sysfs
>>   do_one_initcall (init/main.c:1296)
>>   ...
>> Kernel panic - not syncing: Fatal exception
>> Kernel Offset: 0x4000000 from 0xffffffff81000000
>> ---[ end Kernel panic - not syncing: Fatal exception ]---
>>
>> It is because previous patch added kobject_put() to release the memory
>> which will call  dmi_sysfs_entry_release() and list_del().
>>
>> However, list_add_tail(entry->list) is called after the error block,
>> so the list_head is uninitialized and cannot be deleted.
>>
>> Move error handling to after list_add_tail to fix this.
>>
>> Fixes: 660ba678f999 ("firmware: dmi-sysfs: Fix memory leak in dmi_sysfs_register_handle")
>> Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
>> ---
>> v1 -> v2:
>> Change fix to moving error handling to after list_add_tail.
>> So that it is consistent with kobject_put(&entry->kobj) in other
>> places.
> <snip>
>
> I got 2 copies of this, which one is correct?

Sorry I accidentally re-sent this, they are all same.

Thanks!

Chen

> thanks,
>
> greg k-h