2011/11/8 Ted Ts'o <tytso@xxxxxxx>:
> On Mon, Nov 07, 2011 at 11:01:51PM +0900, Namjae Jeon wrote:
>> Fix NULL pointer dereference from orig_data in fill_super and remount.
>>
>> Signed-off-by: Namjae Jeon <linkinjeon@xxxxxxxxx>
>
> Um, did you even try to test this patch before submitting it?
>
> #1: kstrdup() return NULL if data is NULL
>
> #2: The kernel's printk and sprintf functions will translate
> sprintf(buf, "%s", NULL) by filling in the string "NULL"
>
> #3: The only use of orig_data is a cosmetic one, of printing out
> the mount options which are passed in.
>
> #4: If the user doesn't specify any mount options, data is NULL, and
> your patch would cause those mounts to fail with ENOMEM.
>
> In summary, there is no problem here; a pendant might complain that
> it's possible for data to be non-NULL, and for orig_data to be null of
> the kstrdup failed, but in that case, other memory allocations done
> later in ext4_fill_super() will almost have certainly failed, so in
> practice won't get as far as the printk.
Hi. Ted.
Sorry, I will make a patch next time after testing. Thanks for your review.
And I checked how to handle this case in other filesystem.
btrfs try to handle like this.
------------------------------------------------------------------------------
if (!options)
goto out;
/*
* strsep changes the string, duplicate it because parse_options
* gets called twice
*/
opts = kstrdup(options, GFP_KERNEL);
if (!opts)
return -ENOMEM;
-------------------------------------------------------------------------------
So I suggest that ext4 try to handle like this.
-------------------------------------------------------------------------------
if(data) {
orig_data = kstrdup(data, GFP_KERNEL);
if(!orig_data)
return ret;
}
-------------------------------------------------------------------------------
I want to know your opinion.
Thanks.
>
> - Ted
>
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