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Subject[PATCH 3.10 097/123] lib/bitmap.c: fix undefined shift in __bitmap_shift_{left|right}()
Date
3.10-stable review patch.  If anyone has any objections, please let me know.

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

From: Jan Kara <jack@suse.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@suse.cz>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
lib/bitmap.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -131,7 +131,9 @@ 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;
}
@@ -172,7 +174,9 @@ 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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