linux-kernel - [PATCH 1/2] crypto: caam - fix gfp allocation flags (part I)

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Date:   Mon, 19 Jun 2017 11:44:45 +0300
From:   Horia Geantă <horia.geanta@....com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        David Gstir <david@...ma-star.at>
CC:     "David S. Miller" <davem@...emloft.net>,
        Dan Douglass <dan.douglass@....com>, <richard@...ma-star.at>,
        Radu Solea <radu.solea@....com>,
        <linux-crypto@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] crypto: caam - fix gfp allocation flags (part I)

Changes in the SW cts (ciphertext stealing) code in
commit 0605c41cc53ca ("crypto: cts - Convert to skcipher")
revealed a problem in the CAAM driver:
when cts(cbc(aes)) is executed and cts runs in SW,
cbc(aes) is offloaded in CAAM; cts encrypts the last block
in atomic context and CAAM incorrectly decides to use GFP_KERNEL
for memory allocation.

Fix this by allowing GFP_KERNEL (sleeping) only when MAY_SLEEP flag is
set, i.e. remove MAY_BACKLOG flag.

We split the fix in two parts - first is sent to -stable, while the
second is not (since there is no known failure case).

Link: http://lkml.kernel.org/g/20170602122446.2427-1-david@sigma-star.at
Cc: <stable@...r.kernel.org> # 4.8+
Reported-by: David Gstir <david@...ma-star.at>
Signed-off-by: Horia Geantă <horia.geanta@....com>
---
 drivers/crypto/caam/caamalg.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/crypto/caam/caamalg.c b/drivers/crypto/caam/caamalg.c
index 398807d1b77e..4ecf92e3b404 100644
--- a/drivers/crypto/caam/caamalg.c
+++ b/drivers/crypto/caam/caamalg.c
@@ -1475,8 +1475,7 @@ static struct ablkcipher_edesc *ablkcipher_edesc_alloc(struct ablkcipher_request
 	struct crypto_ablkcipher *ablkcipher = crypto_ablkcipher_reqtfm(req);
 	struct caam_ctx *ctx = crypto_ablkcipher_ctx(ablkcipher);
 	struct device *jrdev = ctx->jrdev;
-	gfp_t flags = (req->base.flags & (CRYPTO_TFM_REQ_MAY_BACKLOG |
-					  CRYPTO_TFM_REQ_MAY_SLEEP)) ?
+	gfp_t flags = (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) ?
 		       GFP_KERNEL : GFP_ATOMIC;
 	int src_nents, mapped_src_nents, dst_nents = 0, mapped_dst_nents = 0;
 	struct ablkcipher_edesc *edesc;
-- 
2.12.0.264.gd6db3f216544