lib/bitmap.c: fix undefined shift in __bitmap_shift_{left|right}()

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
index cd250a2e14cb..b499ab6ada29 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -131,7 +131,9 @@ void __bitmap_shift_right(unsigned long *dst,
                 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 *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;
         }