The error value is -2, but at this point ret has already been set to
some running answer and must be reset to -2.
(This is unreachable. BN_rshift only fails on caller or malloc error,
and it doesn't need to malloc when running in-place.)
Change-Id: I33930da84b00d1906bdee9d09b9504ea8121fac4
Reviewed-on: https://boringssl-review.googlesource.com/12681
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
9434b6bb5b