linux-kernel - [PATCH 3.2 03/60] regmap: debugfs: Ensure we don't underflow when printing access masks

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Message-ID: <lsq.1447551945.484871051@decadent.org.uk>
Date:	Sun, 15 Nov 2015 01:45:45 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Rasmus Villemoes" <linux@...musvillemoes.dk>,
	"Mark Brown" <broonie@...nel.org>
Subject: [PATCH 3.2 03/60] regmap: debugfs: Ensure we don't underflow when
 printing access masks

3.2.73-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Mark Brown <broonie@...nel.org>

commit b763ec17ac762470eec5be8ebcc43e4f8b2c2b82 upstream.

If a read is attempted which is smaller than the line length then we may
underflow the subtraction we're doing with the unsigned size_t type so
move some of the calculation to be additions on the right hand side
instead in order to avoid this.

Reported-by: Rasmus Villemoes <linux@...musvillemoes.dk>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/base/regmap/regmap-debugfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -140,7 +140,7 @@ static ssize_t regmap_access_read_file(s
 		/* If we're in the region the user is trying to read */
 		if (p >= *ppos) {
 			/* ...but not beyond it */
-			if (buf_pos >= count - 1 - tot_len)
+			if (buf_pos + tot_len + 1 >= count)
 				break;
 
 			/* Format the register */

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