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 07:18:58 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Chen Zhongjin <chenzhongjin@...wei.com>
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

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?

thanks,

greg k-h