linux-kernel - [PATCH] bitmap: Fix undefined shift in __bitmap_shift

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Date:	Wed, 22 Oct 2014 14:43:51 +0200
From:	Jan Kara <jack@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	stable@...r.kernel.org
Subject: [PATCH] bitmap: Fix undefined shift in __bitmap_shift_left()

It __bitmap_shift_left() is asked to shift by a multiple of
BITS_PER_LONG, it will try to shift a long value by BITS_PER_LONG bits
which is undefined. Change the function to take this into account.

Coverity-id: 1192175
CC: Rasmus Villemoes <linux@...musvillemoes.dk>
CC: stable@...r.kernel.org
Signed-off-by: Jan Kara <jack@...e.cz>
---
 lib/bitmap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index cd250a2e14cb..02a8a439fcc7 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -172,7 +172,9 @@ void __bitmap_shift_left(unsigned long *dst,
 		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;
 	}
-- 
1.8.1.4

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