From 9bde916bc73255dcee3d8aded990443675daa707 Mon Sep 17 00:00:00 2001
From: Chen Gang <gang.chen@asianux.com>
Date: Wed, 3 Jul 2013 15:02:36 -0700
Subject: [PATCH] mm/nommu.c: add additional check for vread() just like
 vwrite() has done

vwrite() checks for overflow. vread() should do the same thing.

Since vwrite() checks the source buffer address, vread() should check
the destination buffer address.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/nommu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/nommu.c b/mm/nommu.c
index 298884dcd6e7..1898b2fe9da5 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -282,6 +282,10 @@ EXPORT_SYMBOL(vmalloc_to_pfn);
 
 long vread(char *buf, char *addr, unsigned long count)
 {
+	/* Don't allow overflow */
+	if ((unsigned long) buf + count < count)
+		count = -(unsigned long) buf;
+
 	memcpy(buf, addr, count);
 	return count;
 }
-- 
2.20.1