Commit 7d38ca3f authored by Andy Polyakov's avatar Andy Polyakov
Browse files

x509v3/v3_purp.c: refine lock-free check in x509v3_cache_extensions. 



Reviewed-by: default avatarKurt Roeckx <kurt@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/6996)
parent a88e328c

crypto/x509v3/v3_purp.c

+10 −6
Original line number Diff line number Diff line
@@ -354,9 +354,11 @@ static void x509v3_cache_extensions(X509 *x) 
    X509_EXTENSION *ex;

    int i;



#ifdef tsan_ld_acq

    /* fast lock-free check, see end of the function for details. */

    if (tsan_load((TSAN_QUALIFIER int *)&x->ex_cached))

    if (tsan_ld_acq((TSAN_QUALIFIER int *)&x->ex_cached))

        return;

#endif



    CRYPTO_THREAD_write_lock(x->lock);

    if (x->ex_flags & EXFLAG_SET) {
@@ -498,13 +500,15 @@ static void x509v3_cache_extensions(X509 *x) 
    }

    x509_init_sig_info(x);

    x->ex_flags |= EXFLAG_SET;

    CRYPTO_THREAD_unlock(x->lock);

#ifdef tsan_st_rel

    tsan_st_rel((TSAN_QUALIFIER int *)&x->ex_cached, 1);

    /*

     * It has to be placed after memory barrier, which is implied by unlock.

     * Worst thing that can happen is that another thread proceeds to lock

     * and checks x->ex_flags & EXFLAGS_SET. See beginning of the function.

     * Above store triggers fast lock-free check in the beginning of the

     * function. But one has to ensure that the structure is "stable", i.e.

     * all stores are visible on all processors. Hence the release fence.

     */

    tsan_store((TSAN_QUALIFIER int *)&x->ex_cached, 1);

#endif

    CRYPTO_THREAD_unlock(x->lock);

}



/*-