[PATCH] bitmap: Fix undefined shift in __bitmap_shift_left()

[Jan Kara]

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 <***@rasmusvillemoes.dk>
CC: ***@vger.kernel.org
Signed-off-by: Jan Kara <***@suse.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;
}

[Jan Kara]

Post by Jan Kara
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

Oops, there's one more occurence of this. I'll send an updated patch.

Honza

Post by Jan Kara
---
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