linux-kernel - [PATCH 1/1] kernel/fork.c: avoid division by zero

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Message-Id: <1424109644-22579-1-git-send-email-xypron.glpk@gmx.de>
Date:	Mon, 16 Feb 2015 19:00:44 +0100
From:	Heinrich Schuchardt <xypron.glpk@....de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Rientjes <rientjes@...gle.com>,
	Kees Cook <keescook@...omium.org>,
	Aaron Tomlin <atomlin@...hat.com>,
	linux-kernel@...r.kernel.org,
	Heinrich Schuchardt <xypron.glpk@....de>
Subject: [PATCH 1/1] kernel/fork.c: avoid division by zero

PAGE_SIZE is not guaranteed to be equal to or less than 8 times the
THREAD_SIZE.

E.g. architecture hexagon may have page size 1M and thread size 4096.

This would lead to a division by zero.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
---
 kernel/fork.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index cf65139..71e2583 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -273,7 +273,8 @@ void __init fork_init(unsigned long mempages)
 	 * value: the thread structures can take up at most half
 	 * of memory.
 	 */
-	max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
+	max_threads = (u64) PAGE_SIZE * (u64) mempages
+		    / (u64) THREAD_SIZE / 8UL;
 
 	/*
 	 * we need to allow at least 20 threads to boot a system
-- 
2.1.4

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