Re: Crash while trying to destroy memory cache with Heimdal 1.4.1rc2

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Narendra

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On Sat, Dec 10, 2011 at 10:56 AM, Love Hörnquist Åstrand <[email protected]> wrote:

> Hello,
>
> Think about krb5_cc_destroy as a krb5_cc_close() combined with delete all
> data.
>
> Hi,
>
> I need some help in understanding the Heimdal KRB5 Memory cache usage.
> In the file 'lib/krb5/test_cc.c ', I see the following line in
> documentation.
>
>  93 /*
>  94  * Check that a closed cc still keeps it data and that it's no longer
>  95  * there when it's destroyed.
>  96  */
>
>
> This checks that if a credential cache doesn't go away on krb5_cc_close()
> and that is really gone when calling krb5_cc_destroy().
>
>
> This implies, that a KRB5 cache needs to be destroyed after it is close,
> or else it will retain the data.
> But if you look at the code, it suggests that ref counting is done and the
> data is freed when you do a close.
> The ref counting can be seen in the file 'lib/krb5/mcache.c ',  in
> following lines:
>
>
> Reference counting is done on the name, so that multiple holders of the
> same cache wont destroy the underlaying handle. The credential data can be
> destroyed though.
>
> So I chose to still do a krb5_cc_destroy to make sure I'm not leaking
> memory in some other scenarios.
> But, when my class tries to do a krb5_cc_destroy() in the destructor, it
> hits an krb5_abortx() in the same file on following line numbers:
>
> 200     if (m->refcnt == 0)
> 201       krb5_abortx(context, "mcc_destroy: refcnt already 0");
> 202
>
>
> krb5_cc_destroy() is an implicit krb5_cc_close().
>
>
> I need some help in understanding the use of KRB5 cache of type MEMORY.
>  Following are the specific questions I need help with:
> 1] Is Krb5 Mem cache data ref-counted or needs to be explicitly destroyed?
>
>
> Its refcounted and the data is destroyed.
>
> 2] While destroying the object, should I use krb5_cc_close() or
> krb5_cc_destroy() or both?
>
>
> krb5_cc_destroy(), destroy lead to the marking the object as dead, and
> when the last reference is dropped, its gone.
> It can be resurected by krb5_cc_initalize().
>
> Love
>
>
>
>