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linux/kernel.h: fix overflow for DIV_ROUND_UP_ULL 

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>
This commit is contained in:
Vinod Koul 2019-06-28 12:07:21 -07:00 committed by Linus Torvalds
parent 1a5f439c7c
commit 8f9fab480c
1 changed files with 2 additions and 1 deletions
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3
include/linux/kernel.h
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@ -93,7 +93,8 @@
#define DIV_ROUND_DOWN_ULL(ll, d) \
({ 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
# define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP_ULL(ll, d)