From 085df42259cba7863cd6ebe5cd0d8492ac5b869e Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.com>
Date: Thu, 6 Dec 2018 10:35:41 +1100
Subject: [PATCH] Grow: avoid overflow in compute_backup_blocks()
Git-commit: 085df42259cba7863cd6ebe5cd0d8492ac5b869e
Patch-mainline: mdadm-4.1+
References: jsc#SLE-10078, jsc#SLE-9348

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>
Signed-off-by: Coly Li <colyli@suse.de>

---
 Grow.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Grow.c b/Grow.c
index 4436a4d6bd4c..76f82c075e38 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;
 }
-- 
2.14.0.rc0.dirty