Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote:
> Anyway, why did you remove the condition on hash_free_result?
> We free the result if it's not needed, not to clear the previous
> hash. So by doing it uncondtionally you will simply end up
> freeing and reallocating the result for no good reason.
The free here:
if (!continuing) {
if ((msg->msg_flags & MSG_MORE))
hash_free_result(sk, ctx);
only happens in the following case:
send(hashfd, "", 0, 0);
send(hashfd, "", 0, MSG_MORE); <--- by this
and the patch changes how this case works if no data is given. In Linus's
tree, it will create a result, init the crypto and finalise it in
hash_sendmsg(); with this patch that case is then handled by hash_recvmsg().
If you consider the following sequence:
send(hashfd, "", 0, 0);
send(hashfd, "", 0, 0);
send(hashfd, "", 0, 0);
send(hashfd, "", 0, 0);
Upstream, the first one will create a result and then each of them will init
and finalise a hash, whereas with my patch, the first one will release any
outstanding result and then none of them will do any crypto ops.
However, as, with my patch hash_sendmsg() no longer calculated a result, it
has to clear the result pointer because the logic inside hash_recvmsg() relies
on the result pointer to indicate that there is a result.
Instead, hash_recvmsg() concocts the result - something it has to be able to
do anyway in case someone calls recvmsg() without first supplying data.
David
