Commit 2656ee5a authored Jun 28, 2019 by Vinod Koul Committed by Greg Kroah-Hartman Jul 21, 2019

linux/kernel.h: fix overflow for DIV_ROUND_UP_ULL

[ Upstream commit 8f9fab480c7a87b10bb5440b5555f370272a5d59 ]

DIV_ROUND_UP_ULL adds the two arguments and then invokes
DIV_ROUND_DOWN_ULL.  But on a 32bit system the addition of two 32 bit
values can overflow.  DIV_ROUND_DOWN_ULL does it correctly and stashes
the addition into a unsigned long long so cast the result to unsigned
long long here to avoid the overflow condition.

[akpm@linux-foundation.org: DIV_ROUND_UP_ULL must be an rval]
Link: http://lkml.kernel.org/r/20190625100518.30753-1-vkoul@kernel.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 9c875e85

include/linux/kernel.h

+2 −1

Original line number	Original line	Diff line number	Diff line
	@@ -118,7 +118,8 @@
	#define DIV_ROUND_DOWN_ULL(ll, d) \		#define DIV_ROUND_DOWN_ULL(ll, d) \
	({ unsigned long long _tmp = (ll); do_div(_tmp, d); _tmp; })		({ unsigned long long _tmp = (ll); do_div(_tmp, d); _tmp; })

	#define DIV_ROUND_UP_ULL(ll, d) DIV_ROUND_DOWN_ULL((ll) + (d) - 1, (d))		#define DIV_ROUND_UP_ULL(ll, d) \
			DIV_ROUND_DOWN_ULL((unsigned long long)(ll) + (d) - 1, (d))

	#if BITS_PER_LONG == 32		#if BITS_PER_LONG == 32
	# define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP_ULL(ll, d)		# define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP_ULL(ll, d)