Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.0 029/123] crypto: chacha-generic - fix use as arm64 no-NEON fallback | Date | Mon, 20 May 2019 14:13:29 +0200 |
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From: Eric Biggers <ebiggers@google.com>
commit 7aceaaef04eaaf6019ca159bc354d800559bba1d upstream.
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: <stable@vger.kernel.org> # v5.0+ Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- crypto/chacha_generic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/crypto/chacha_generic.c +++ b/crypto/chacha_generic.c @@ -52,7 +52,7 @@ static int chacha_stream_xor(struct skci 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);
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