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| author | Yury Norov <yury.norov@gmail.com> | 2022-04-28 13:51:12 -0700 |
|---|---|---|
| committer | Yury Norov <yury.norov@gmail.com> | 2022-06-03 06:52:58 -0700 |
| commit | e041e0ac53dd52d2d201aa87edc3adaca1085299 (patch) | |
| tree | 6c77b6ff337b35827d55e3d1770798e815ff97ea | |
| parent | 6d7131bd52b3e0dd068a0067e5584b3f36cf17eb (diff) | |
| download | linux-e041e0ac53dd52d2d201aa87edc3adaca1085299.tar.bz2 | |
lib/bitmap: extend comment for bitmap_(from,to)_arr32()
On LE systems bitmaps are naturally ordered, therefore we can potentially
use bitmap_copy routines when converting from 32-bit arrays, even if host
system is 64-bit. But it may lead to out-of-bond access due to unsafe
typecast, and the bitmap_(from,to)_arr32 comment doesn't explain that
clearly
CC: Alexander Gordeev <agordeev@linux.ibm.com>
CC: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
CC: Christian Borntraeger <borntraeger@linux.ibm.com>
CC: Claudio Imbrenda <imbrenda@linux.ibm.com>
CC: David Hildenbrand <david@redhat.com>
CC: Heiko Carstens <hca@linux.ibm.com>
CC: Janosch Frank <frankja@linux.ibm.com>
CC: Rasmus Villemoes <linux@rasmusvillemoes.dk>
CC: Sven Schnelle <svens@linux.ibm.com>
CC: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
| -rw-r--r-- | include/linux/bitmap.h | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 7dba0847510c..afcf7b8dddd1 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -264,8 +264,12 @@ static inline void bitmap_copy_clear_tail(unsigned long *dst, } /* - * On 32-bit systems bitmaps are represented as u32 arrays internally, and - * therefore conversion is not needed when copying data from/to arrays of u32. + * On 32-bit systems bitmaps are represented as u32 arrays internally. On LE64 + * machines the order of hi and lo parts of numbers match the bitmap structure. + * In both cases conversion is not needed when copying data from/to arrays of + * u32. But in LE64 case, typecast in bitmap_copy_clear_tail() may lead + * to out-of-bound access. To avoid that, both LE and BE variants of 64-bit + * architectures are not using bitmap_copy_clear_tail(). */ #if BITS_PER_LONG == 64 void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf, |