From 9bbca12514f329a54e11ed37f572eaecb19dd147 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Mon, 9 Oct 2017 23:30:02 +0800
Subject: [PATCH] crypto: shash - Fix zero-length shash ahash digest crash
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commit b61907bb42409adf9b3120f741af7c57dd7e3db2 upstream.

The shash ahash digest adaptor function may crash if given a
zero-length input together with a null SG list.  This is because
it tries to read the SG list before looking at the length.

This patch fixes it by checking the length first.

Reported-by: Stephan Müller<smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Stephan Müller <smueller@chronox.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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Reading git-format-patch failed