From 085df42259cba7863cd6ebe5cd0d8492ac5b869e Mon Sep 17 00:00:00 2001

From: NeilBrown <neilb@suse.com>

Date: Thu, 6 Dec 2018 10:35:41 +1100

Subject: [RHEL7.7 PATCH 08/24] Grow: avoid overflow in compute_backup_blocks()

With a chunk size of 16Meg and data drive count of 8,

this calculate can easily overflow the 'int' type that

is used for the multiplications.

So force it to use "long" instead.

Reported-and-tested-by: Ed Spiridonov <edo.rus@gmail.com>

Signed-off-by: NeilBrown <neilb@suse.com>

Signed-off-by: Jes Sorensen <jsorensen@fb.com>

---

 Grow.c | 3 ++-

 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Grow.c b/Grow.c

index 4436a4d..76f82c0 100644

--- a/Grow.c

+++ b/Grow.c

@@ -1196,7 +1196,8 @@ unsigned long compute_backup_blocks(int nchunk, int ochunk,

 	/* Find GCD */

 	a = GCD(a, b);

 	/* LCM == product / GCD */

-	blocks = (ochunk/512) * (nchunk/512) * odata * ndata / a;

+	blocks = (unsigned long)(ochunk/512) * (unsigned long)(nchunk/512) *

+		odata * ndata / a;

 	return blocks;

 }

-- 

2.7.5