linux-kernel - [PATCH 3.2 095/164] lib/bitmap.c: fix undefined shift in __bitmap_shift

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Date:	Fri, 12 Dec 2014 06:14:25 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Rasmus Villemoes" <linux@...musvillemoes.dk>,
	"Jan Kara" <jack@...e.cz>
Subject: [PATCH 3.2 095/164] lib/bitmap.c: fix undefined shift in
 __bitmap_shift_{left|right}()

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

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

From: Jan Kara <jack@...e.cz>

commit ea5d05b34aca25c066e0699512d0ffbd8ee6ac3e upstream.

If __bitmap_shift_left() or __bitmap_shift_right() are asked to shift by
a multiple of BITS_PER_LONG, they will try to shift a long value by
BITS_PER_LONG bits which is undefined.  Change the functions to avoid
the undefined shift.

Coverity id: 1192175
Coverity id: 1192174
Signed-off-by: Jan Kara <jack@...e.cz>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 lib/bitmap.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -129,7 +129,9 @@ void __bitmap_shift_right(unsigned long
 		lower = src[off + k];
 		if (left && off + k == lim - 1)
 			lower &= mask;
-		dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem;
+		dst[k] = lower >> rem;
+		if (rem)
+			dst[k] |= upper << (BITS_PER_LONG - rem);
 		if (left && k == lim - 1)
 			dst[k] &= mask;
 	}
@@ -170,7 +172,9 @@ void __bitmap_shift_left(unsigned long *
 		upper = src[k];
 		if (left && k == lim - 1)
 			upper &= (1UL << left) - 1;
-		dst[k + off] = lower  >> (BITS_PER_LONG - rem) | upper << rem;
+		dst[k + off] = upper << rem;
+		if (rem)
+			dst[k + off] |= lower >> (BITS_PER_LONG - rem);
 		if (left && k + off == lim - 1)
 			dst[k + off] &= (1UL << left) - 1;
 	}

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