lib: bitmap: add missing mask in bitmap_and

Apparently, bitmap_and is supposed to return whether the new bitmap is
empty.  But it didn't take potential garbage bits in the last word into
account.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
index faaf7206d4cf..ce2ec80bf431 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -185,11 +185,14 @@ int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
                                 const unsigned long *bitmap2, unsigned int bits)
 {
         unsigned int k;
-        unsigned int nr = BITS_TO_LONGS(bits);
+        unsigned int lim = bits/BITS_PER_LONG;
         unsigned long result = 0;
 
-        for (k = 0; k < nr; k++)
+        for (k = 0; k < lim; k++)
                 result |= (dst[k] = bitmap1[k] & bitmap2[k]);
+        if (bits % BITS_PER_LONG)
+                result |= (dst[k] = bitmap1[k] & bitmap2[k] &
+                           BITMAP_LAST_WORD_MASK(bits));
         return result != 0;
 }
 EXPORT_SYMBOL(__bitmap_and);