Fix race condition in ssl_parse_serverhello_tlsext

CVE-2014-3509

(Imported from upstream's 92aa73bcbfad44f9dd7997ae51537ac5d7dc201e)

Change-Id: Ibc681897251081ae5ebfea0ff6ca9defd73fe0f5
Reviewed-on: https://boringssl-review.googlesource.com/1441
Reviewed-by: David Benjamin <davidben@chromium.org>
Reviewed-by: Adam Langley <agl@google.com>
1 file changed