Re: [patch] [SCSI] libosd: check for kzalloc() failure

[walter harms <wharms@bfs.de>]

Am 30.01.2013 10:51, schrieb Benny Halevy:
> On Wed, Jan 30, 2013 at 10:57 AM, walter harms <wharms@bfs.de> wrote:
>>
>>
>> Am 30.01.2013 09:27, schrieb Dan Carpenter:
>>> On Wed, Jan 30, 2013 at 09:15:43AM +0100, walter harms wrote:
>>>>
>>>>
>>>> Am 30.01.2013 08:06, schrieb Dan Carpenter:
>>>>> There wasn't any error handling for this kzalloc().
>>>>>
>>>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>>>>
>>>>> diff --git a/drivers/scsi/osd/osd_initiator.c b/drivers/scsi/osd/osd_initiator.c
>>>>> index c06b8e5..d8293f2 100644
>>>>> --- a/drivers/scsi/osd/osd_initiator.c
>>>>> +++ b/drivers/scsi/osd/osd_initiator.c
>>>>> @@ -144,6 +144,10 @@ static int _osd_get_print_system_info(struct osd_dev *od,
>>>>>     odi->osdname_len = get_attrs[a].len;
>>>>>     /* Avoid NULL for memcmp optimization 0-length is good enough */
>>>>>     odi->osdname = kzalloc(odi->osdname_len + 1, GFP_KERNEL);
>>>>> +   if (!odi->osdname) {
>>>>> +           ret = -ENOMEM;
>>>>> +           goto out;
>>>>> +   }
>>>>>     if (odi->osdname_len)
>>>>>             memcpy(odi->osdname, get_attrs[a].val_ptr, odi->osdname_len);
>>>>>     OSD_INFO("OSD_NAME               [%s]\n", odi->osdname);
>>>>> --
>>>>
>>>> this looks like strdup() ?
>>>>
>>>
>>> Maybe?  It's a funny thing going on with the NUL terminator and I
>>> don't understand what the comment is about.
>>>
>>> It appears that normally "get_attrs[a].val_ptr" is a NUL terminated
>>> string but "get_attrs[a].len" does not count the terminator.
>>>
>>> Odd.
>>>
>> i have no clue what the programmer was thinking. if i read this correct
>> osdname is u8 *osdname; so a simple strdup() or strndup() would be ok
>> the comment seems to indicate that get_attrs[a].val_ptr could be NULL
>> but where is the check ?
>> Perhaps they are not using ascii here ? then a memdup(get_attrs[a].len)
>> would be better.
> 
> There are subtle differences between kstrdup or kmemdup and this implementation.
> 
> kmemdup is problematic as get_attrs[a].val_ptr does not contain the
> NUL terminator

ok, i understand - but can we assume that we are talking ascii here ?

> In the following case:
> if get_attrs[a].len = 0
> then get_attrs[a].val_ptr = NULL
> 
> The end result should be
> odi->osdname_len = 0
> odi->osdname = kzalloc(1, GFP_KERNEL);
> 
> while with kstrdup, odi->osdname will end up being NULL
> as it's input arg "s" is NULL.
> 

and you want the argument to be "" ?
May i ask why ? kfree() can handle NULL and kprintf() (-family) also.

re,
 wh


> Benny
> 
>>
>> re,
>>  wh
>>
>>
> 
>