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>

diff --git a/lib/bitmap.c b/lib/bitmap.c
index cd250a2..b499ab6 100644 (file)
--- 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;
        }