From 9a156466147b61504f4cbe97ea503e67c21e117a Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 25 Sep 2019 16:46:20 -0700
Subject: [PATCH] strscpy: reject buffer sizes larger than INT_MAX

As already done for snprintf(), add a check in strscpy() for giant (i.e.
likely negative and/or miscalculated) copy sizes, WARN, and error out.

Link: http://lkml.kernel.org/r/201907260928.23DE35406@keescook
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Joe Perches <joe@perches.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Yann Droneaud <ydroneaud@opteya.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Stephen Kitt <steve@sk2.org>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 lib/string.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/string.c b/lib/string.c
index f7bc10da4259..cd7a10c19210 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -183,7 +183,7 @@ ssize_t strscpy(char *dest, const char *src, size_t count)
 	size_t max = count;
 	long res = 0;
 
-	if (count == 0)
+	if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
 		return -E2BIG;
 
 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS