diff options
| author | Rasmus Villemoes | 2018-10-30 15:04:59 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2018-10-31 08:54:12 -0700 |
| commit | 7275b097851a5e2e0dd4da039c7e96b59ac5314e (patch) | |
| tree | e5242c165fd62279c74f1951a93f23e427203d0a /include | |
| parent | 696e4219237b4cac48b5145f497f4840bb5e3391 (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.h | 7 |
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) { |