On Thu, 2012-12-20 at 16:14 +0100, Pavel Březina wrote:
On 12/20/2012 02:20 PM, Simo Sorce wrote:
> On Thu, 2012-12-20 at 12:29 +0100, Pavel Březina wrote:
>> On 12/20/2012 06:10 AM, Simo Sorce wrote:
>>> -static errno_t sss_mc_get_record(struct sss_mc_ctx *mcc,
>>> +static errno_t sss_mc_get_record(struct sss_mc_ctx **_mcc,
>>> size_t rec_len,
>>> struct sized_string *key,
>>> struct sss_mc_rec **_rec)
>>> {
>>> + struct sss_mc_ctx *mcc = *_mcc;
>>> struct sss_mc_rec *old_rec = NULL;
>>> struct sss_mc_rec *rec;
>>> int old_slots;
>>> @@ -424,6 +425,16 @@ static errno_t sss_mc_get_record(struct sss_mc_ctx
*mcc,
>>> /* we are going to use more space, find enough free slots */
>>> ret = sss_mc_find_free_slots(mcc, num_slots, &base_slot);
>>> if (ret != EOK) {
>>> + if (ret == EFAULT) {
>>> + TALLOC_CTX *parent;
>>> + DEBUG(SSSDBG_CRIT_FAILURE,
>>> + ("Fatal internal mmap cache error, invalidating
cache!\n"));
>>> + parent = talloc_parent(mcc);
>>> + if (parent == NULL) {
>>> + talloc_zfree(*_mcc);
>>> + }
>>> + (void)sss_mmap_cache_reinit(parent, -1, -1, _mcc);
>>> + }
>>> return ret;
>>> }
>>
>> Hi,
>>
>> Is if (parent == NULL) only precaution or can it actually happen?
>
> Only a precaution, all the callers use an actual memory context.
>
>> If you talloc_zfree(*_mcc) then you will hit EINVAL in reinit() and the
>> cache won't be reinitialized. Is this intentional? If so, can you
>> comment it in the code?
>
> Well it was not intentional I meant to return after the free.
> However I am wondering if we should really care ...
>
> If the caller had NULL as the parent something may have gone wrong, but
> at worst we will leak a few bytes... maybe I shouldn't consider a NULL
> parent as an error after all. Opinions ?
>
> Simo.
>
Does the memory cache require a parent context for some reason (do you
manipulate with the parent within the cache)?
If not I think you should not take care whether is has a parent or not.
For what we know, it may be intentional by the caller. Otherwise you
should check if mem_ctx != NULL in init().
Looking into the init() function I found out that you are using wrong
context:
mc_ctx->name = talloc_strdup(mem_ctx, name);
if (!mc_ctx->name) {
ret = ENOMEM;
goto done;
}
It should say mc_ctx not mem_ctx.
Nice catch.
I also realized that the reinit() function uses talloc_free() instead of
talloc_zfree() on the mc_ctx which would leave a wild pointer to freed
memory in the caller should the init() fail.
So in the attached patch I fixed all this and removed any check about
the talloc_parent(), we just trust it returns the correct value and the
caller did a sensible thing with the first init()
Simo.
--
Simo Sorce * Red Hat, Inc * New York