lib: bitmap: add missing mask in bitmap_andnot

Apparently, bitmap_andnot 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>

2 files changed, 6 insertions, 3 deletions

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 3399a9ecd991..e1c8d080c427 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -217,7 +217,7 @@ static inline int bitmap_andnot(unsigned long *dst, const unsigned long *src1,
                         const unsigned long *src2, unsigned int nbits)
 {
         if (small_const_nbits(nbits))
-                return (*dst = *src1 & ~(*src2)) != 0;
+                return (*dst = *src1 & ~(*src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
         return __bitmap_andnot(dst, src1, src2, nbits);
 }
 
diff --git a/lib/bitmap.c b/lib/bitmap.c
index ce2ec80bf431..1e031f2c9aba 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -223,11 +223,14 @@ int __bitmap_andnot(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_andnot);