From 7aceaaef04eaaf6019ca159bc354d800559bba1d Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 12 Mar 2019 22:12:45 -0700 Subject: [PATCH] crypto: chacha-generic - fix use as arm64 no-NEON fallback The arm64 implementations of ChaCha and XChaCha are failing the extra crypto self-tests following my patches to test the !may_use_simd() code paths, which previously were untested. The problem is as follows: When !may_use_simd(), the arm64 NEON implementations fall back to the generic implementation, which uses the skcipher_walk API to iterate through the src/dst scatterlists. Due to how the skcipher_walk API works, walk.stride is set from the skcipher_alg actually being used, which in this case is the arm64 NEON algorithm. Thus walk.stride is 5*CHACHA_BLOCK_SIZE, not CHACHA_BLOCK_SIZE. This unnecessarily large stride shouldn't cause an actual problem. However, the generic implementation computes round_down(nbytes, walk.stride). round_down() assumes the round amount is a power of 2, which 5*CHACHA_BLOCK_SIZE is not, so it gives the wrong result. This causes the following case in skcipher_walk_done() to be hit, causing a WARN() and failing the encryption operation: if (WARN_ON(err)) { /* unexpected case; didn't process all bytes */ err = -EINVAL; goto finish; } Fix it by rounding down to CHACHA_BLOCK_SIZE instead of walk.stride. (Or we could replace round_down() with rounddown(), but that would add a slow division operation every time, which I think we should avoid.) Fixes: 2fe55987b262 ("crypto: arm64/chacha - use combined SIMD/ALU routine for more speed") Cc: # v5.0+ Signed-off-by: Eric Biggers Reviewed-by: Ard Biesheuvel Signed-off-by: Herbert Xu --- crypto/chacha_generic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/crypto/chacha_generic.c b/crypto/chacha_generic.c index 35b583101f4f..90ec0ec1b4f7 100644 --- a/crypto/chacha_generic.c +++ b/crypto/chacha_generic.c @@ -52,7 +52,7 @@ static int chacha_stream_xor(struct skcipher_request *req, unsigned int nbytes = walk.nbytes; if (nbytes < walk.total) - nbytes = round_down(nbytes, walk.stride); + nbytes = round_down(nbytes, CHACHA_BLOCK_SIZE); chacha_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr, nbytes, ctx->nrounds); -- 2.30.2