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

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Date: Mon, 22 Apr 2024 19:31:47 +0800
From: Baokun Li <libaokun1@...wei.com>
To: Jingbo Xu <jefflexu@...ux.alibaba.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>,
	Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH -next v3 1/2] erofs: get rid of erofs_fs_context

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)

Thank you very much for the review!
-- 
With Best Regards,
Baokun Li