linux-kernel - Re: [PATCH -next v3 1/2] erofs: get rid of erofs_fs

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Message-ID: <2a7edcc0-6890-412d-b2ba-8bfa8694beeb@linux.alibaba.com>
Date: Mon, 22 Apr 2024 19:39:56 +0800
From: Jingbo Xu <jefflexu@...ux.alibaba.com>
To: Baokun Li <libaokun1@...wei.com>, linux-erofs@...ts.ozlabs.org
Cc: xiang@...nel.org, chao@...nel.org, huyue2@...lpad.com,
 viro@...iv.linux.org.uk, brauner@...nel.org, linux-kernel@...r.kernel.org,
 yangerkun@...wei.com, houtao1@...wei.com
Subject: Re: [PATCH -next v3 1/2] erofs: get rid of erofs_fs_context



On 4/22/24 7:31 PM, Baokun Li wrote:
> Hi Jingbo,
> 
> On 2024/4/22 18:25, Jingbo Xu wrote:
>>
>> On 4/19/24 8:36 PM, Baokun Li wrote:
>>
>>> @@ -761,12 +747,15 @@ static void erofs_free_dev_context(struct
>>> erofs_dev_context *devs)
>>>     static void erofs_fc_free(struct fs_context *fc)
>>>   {
>>> -    struct erofs_fs_context *ctx = fc->fs_private;
>>> +    struct erofs_sb_info *sbi = fc->s_fs_info;
>>> +
>>> +    if (!sbi)
>>> +        return;
>>
>> This is the only difference comparing to the original code literally.
>> Is there any chance that fc->s_fs_info can be NULL when erofs_fc_free()
>> is called?
>>
>> Otherwise looks good to me.
>>
> When sget_fc() executes successfully, fc->s_fs_info is set to NULL,
> so the following NULL pointer dereference may occur:
> 
> do_new_mount
>   vfs_get_tree
>     erofs_fc_get_tree
>       get_tree_bdev
>         sget_dev
>           sget_fc
>             s = alloc_super
>             s->s_fs_info = fc->s_fs_info;
>             fc->s_fs_info = NULL;
>         fill_super
>         // return error
>         deactivate_locked_super
>           kfree(sbi);
>   put_fs_context
>     sbi = fc->s_fs_info
>     kfree(sbi->fsid)
> 

Alright, fc->s_fs_info is transferred to s->s_fs_info and set to NULL.

Feel free to add:

Reviewed-by: Jingbo Xu <jefflexu@...ux.alibaba.com>

-- 
Thanks,
Jingbo