[patch] cifs: integer overflow in parse_dacl()

[Steve French]

On Wed, Jan 11, 2012 at 9:50 AM, Shirish Pargaonkar
<shirishpargaonkar at gmail.com> wrote:
> On Wed, Jan 11, 2012 at 1:46 AM, Dan Carpenter <dan.carpenter at oracle.com> wrote:
>> On 32 bit systems num_aces * sizeof(struct cifs_ace *) could overflow
>> leading to a smaller ppace buffer than we expected.
>>
>> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
>>
>> diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
>> index 72ddf23..c1b2544 100644
>> --- a/fs/cifs/cifsacl.c
>> +++ b/fs/cifs/cifsacl.c
>> @@ -909,6 +909,8 @@ static void parse_dacl(struct cifs_acl *pdacl, char *end_of_acl,
>>                umode_t group_mask = S_IRWXG;
>>                umode_t other_mask = S_IRWXU | S_IRWXG | S_IRWXO;
>>
>> +               if (num_aces > ULONG_MAX / sizeof(struct cifs_ace *))
>
> Should an error/warning (like cifs client can't handle these many aces or
> possible erroneous number of aces sent by server etc.) be logged before
> returning?
>
>> +                       return;
>>                ppace = kmalloc(num_aces * sizeof(struct cifs_ace *),
>>                                GFP_KERNEL);
>>                if (!ppace) {

Perhaps.   Also note that you would overflow maximum smb size if num
aces is huge
so would you have even gotten this far?

-- 
Thanks,

Steve