Commit 1762818f authored Oct 25, 2020 by Arvind Sankar Committed by Herbert Xu Oct 30, 2020

crypto: lib/sha256 - Use memzero_explicit() for clearing state



Without the barrier_data() inside memzero_explicit(), the compiler may
optimize away the state-clearing if it can tell that the state is not
used afterwards. At least in lib/crypto/sha256.c:__sha256_final(), the
function can get inlined into sha256(), in which case the memset is
optimized away.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

parent 383e8a82

lib/crypto/sha256.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -265,7 +265,7 @@ static void __sha256_final(struct sha256_state sctx, u8 out, int digest_words)
	put_unaligned_be32(sctx->state[i], &dst[i]);		put_unaligned_be32(sctx->state[i], &dst[i]);

	/* Zeroize sensitive information. */		/* Zeroize sensitive information. */
	memset(sctx, 0, sizeof(*sctx));		memzero_explicit(sctx, sizeof(*sctx));
	}		}

	void sha256_final(struct sha256_state sctx, u8 out)		void sha256_final(struct sha256_state sctx, u8 out)