linux-kernel - [PATCH v2 1/5] MPI: fix off by one in mpi_read_raw_from

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Message-ID: <3192672.E3TvJmsW94@myon.chronox.de>
Date:	Sun, 18 Oct 2015 12:45:18 +0200
From:	Stephan Mueller <smueller@...onox.de>
To:	herbert@...dor.apana.org.au
Cc:	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: [PATCH v2 1/5] MPI: fix off by one in mpi_read_raw_from_sgl

The patch fixes the analysis of the input data which contains an off
by one.

The issue is visible when the SGL contains one byte per SG entry.
The code for checking for zero bytes does not operate on the data byte.

Signed-off-by: Stephan Mueller <smueller@...onox.de>
---
 lib/mpi/mpicoder.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index c20ef27..c7e0a70 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -446,8 +446,11 @@ MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int len)
 		const u8 *buff = sg_virt(sg);
 		int len = sg->length;
 
-		while (len-- && !*buff++)
+		while (len && !*buff) {
 			lzeros++;
+			len--;
+			buff++;
+		}
 
 		if (len && *buff)
 			break;
-- 
2.5.0


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