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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2018-10-30 15:04:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-10-31 08:54:12 -0700
commit7275b097851a5e2e0dd4da039c7e96b59ac5314e (patch)
treee5242c165fd62279c74f1951a93f23e427203d0a /include
parent696e4219237b4cac48b5145f497f4840bb5e3391 (diff)
linux/bitmap.h: handle constant zero-size bitmaps correctly
The static inlines in bitmap.h do not handle a compile-time constant nbits==0 correctly (they dereference the passed src or dst pointers, despite only 0 words being valid to access). I had the 0-day buildbot chew on a patch [1] that would cause build failures for such cases without complaining, suggesting that we don't have any such users currently, at least for the 70 .config/arch combinations that was built. Should any turn up, make sure they use the out-of-line versions, which do handle nbits==0 correctly. This is of course not the most efficient, but it's much less churn than teaching all the static inlines an "if (zero_const_nbits())", and since we don't have any current instances, this doesn't affect existing code at all. [1] lkml.kernel.org/r/20180815085539.27485-1-linux@rasmusvillemoes.dk Link: http://lkml.kernel.org/r/20180818131623.8755-3-linux@rasmusvillemoes.dk Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> Cc: Yury Norov <ynorov@caviumnetworks.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Sudeep Holla <sudeep.holla@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/bitmap.h7
1 files changed, 6 insertions, 1 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index acf5e8df3504..a9805bacbd7c 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -204,8 +204,13 @@ extern int bitmap_print_to_pagebuf(bool list, char *buf,
#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
#define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
+/*
+ * The static inlines below do not handle constant nbits==0 correctly,
+ * so make such users (should any ever turn up) call the out-of-line
+ * versions.
+ */
#define small_const_nbits(nbits) \
- (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG)
+ (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0)
static inline void bitmap_zero(unsigned long *dst, unsigned int nbits)
{