linux-kernel - [PATCH 3.14 01/17] crypto: caam - fix RNG buffer cache alignment

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Date:	Fri, 26 Jun 2015 18:08:23 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Steve Cornelius <steve.cornelius@...escale.com>,
	Victoria Milhoan <vicki.milhoan@...escale.com>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 3.14 01/17] crypto: caam - fix RNG buffer cache alignment

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steve Cornelius <steve.cornelius@...escale.com>

commit 412c98c1bef65fe7589f1300e93735d96130307c upstream.

The hwrng output buffers (2) are cast inside of a a struct (caam_rng_ctx)
allocated in one DMA-tagged region. While the kernel's heap allocator
should place the overall struct on a cacheline aligned boundary, the 2
buffers contained within may not necessarily align. Consenquently, the ends
of unaligned buffers may not fully flush, and if so, stale data will be left
behind, resulting in small repeating patterns.

This fix aligns the buffers inside the struct.

Note that not all of the data inside caam_rng_ctx necessarily needs to be
DMA-tagged, only the buffers themselves require this. However, a fix would
incur the expense of error-handling bloat in the case of allocation failure.

Signed-off-by: Steve Cornelius <steve.cornelius@...escale.com>
Signed-off-by: Victoria Milhoan <vicki.milhoan@...escale.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/crypto/caam/caamrng.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/crypto/caam/caamrng.c
+++ b/drivers/crypto/caam/caamrng.c
@@ -56,7 +56,7 @@

 /* Buffer, its dma address and lock */
 struct buf_data {
-	u8 buf[RN_BUF_SIZE];
+	u8 buf[RN_BUF_SIZE] ____cacheline_aligned;
 	dma_addr_t addr;
 	struct completion filled;
 	u32 hw_desc[DESC_JOB_O_LEN];

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