Re: Fwd: [Bug 69841] New: "double free or corruption" with mod_socache_dbm (socache_dbm_retrieve() + database_cleanup())

On 10/7/25 11:50 AM, Joe Orton wrote:
> On Tue, Oct 07, 2025 at 10:45:27AM +0100, Joe Orton wrote:
>> There should already be a global lock held by API consumer, since the 
>> socache provider is marked with AP_SOCACHE_FLAG_NOTMPSAFE. It looks like 
>> mod_authn_socache is protecting entry to the socache provider inside a 
>> global mutex without checking that flag - overkill but should be safe.
> 
> Ah, not true, it only does it for ->store(). The ->retrieve() calls are 
> then unsafe and racy, that's definitely a bug.

Your proposal would be to setup check_password in mod_authn_socache in a similar way
to ap_authn_cache_store?
Hence wrapping the ->retrieve in a apr_global_mutex_trylock / apr_global_mutex_unlock.
I guess we can still use apr_global_mutex_trylock and return AUTH_USER_NOT_FOUND in case
we do not get the lock?


Regards

Rüdiger