Re: Race observed in if_nametoindex function (not MT-Safe)

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On Mon, Sep 13, 2021 at 11:15 AM pgowda cve via Libc-help
<libc-help@sourceware.org> wrote:
>
> Hi,
>
> The race and assert-triggering was observed in if_nametoindex function.
> It calls __opensock, which contains two static variables (last_type,
> last_family)
> that can race, triggering an assert on line 63 of opensock.c.
> The variables are set in the reverse order to which they are checked.
> Since there is no synchronization between these variables, should the function
> not be made MT-Safe.
>
> The patch was originally posted at:-
> https://sourceware.org/pipermail/libc-alpha/2014-January/048052.html
> It mentions the function as MT-Safe but race was observed.
>
> We may need a memory barrier (atomic_[read|write]_barrier() ? ) to
> ensure that the
> compiler doesn't re-order assembly instructions and has last_family be
> set before last_type.
>
> Environment
> Observed during a system restart when the processes start up and
> software calls if_nametoindex from multiple threads.
> GLIBC was dynamically Linked.
>
> Regards,
> pgowda

I agree, I haved opened
https://sourceware.org/bugzilla/show_bug.cgi?id=28353 to track it.
Thanks for reporting it.