releases/4.4.170/crypto-x86-chacha20-avoid-sleeping-with-preemption-disabled.patch

From ebiggers@kernel.org  Thu Jan 10 20:09:51 2019
From: Eric Biggers <ebiggers@kernel.org>
Date: Mon,  7 Jan 2019 15:15:59 -0800
Subject: crypto: x86/chacha20 - avoid sleeping with preemption disabled
To: stable@vger.kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-crypto@vger.kernel.org, Martin Willi <martin@strongswan.org>, Ard Biesheuvel <ard.biesheuvel@linaro.org>
Message-ID: <20190107231559.13357-1-ebiggers@kernel.org>


From: Eric Biggers <ebiggers@google.com>

In chacha20-simd, clear the MAY_SLEEP flag in the blkcipher_desc to
prevent sleeping with preemption disabled, under kernel_fpu_begin().

This was fixed upstream incidentally by a large refactoring,
commit 9ae433bc79f9 ("crypto: chacha20 - convert generic and x86
versions to skcipher").  But syzkaller easily trips over this when
running on older kernels, as it's easily reachable via AF_ALG.
Therefore, this patch makes the minimal fix for older kernels.

Fixes: c9320b6dcb89 ("crypto: chacha20 - Add a SSSE3 SIMD variant for x86_64")
Cc: linux-crypto@vger.kernel.org
Cc: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/crypto/chacha20_glue.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/x86/crypto/chacha20_glue.c
+++ b/arch/x86/crypto/chacha20_glue.c
@@ -77,6 +77,7 @@ static int chacha20_simd(struct blkciphe
 
 	blkcipher_walk_init(&walk, dst, src, nbytes);
 	err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);
+	desc->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 
 	crypto_chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);