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authorYury Norov <yury.norov@gmail.com>2022-04-28 13:51:12 -0700
committerYury Norov <yury.norov@gmail.com>2022-06-03 06:52:58 -0700
commite041e0ac53dd52d2d201aa87edc3adaca1085299 (patch)
tree6c77b6ff337b35827d55e3d1770798e815ff97ea /include
parent6d7131bd52b3e0dd068a0067e5584b3f36cf17eb (diff)
downloadlinux-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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/bitmap.h8
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,