[PATCH] cpumask: fix double string traverse in cpumask_parse

From: Yury Norov <yury.norov@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Amritha Nambiar <amritha.nambiar@intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	Tejun Heo <tj@kernel.org>, Willem de Bruijn <willemb@google.com>
Cc: Yury Norov <ynorov@marvell.com>,
	Yury Norov <yury.norov@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH] cpumask: fix double string traverse in cpumask_parse
Date: Tue,  9 Apr 2019 13:42:08 -0700	[thread overview]
Message-ID: <20190409204208.12190-1-ynorov@marvell.com> (raw)

From: Yury Norov <ynorov@marvell.com>

cpumask_parse() finds first occurrence of either \n or \0 by calling
strchr() and strlen(). We can do it better with a single call of
strchrnul().

Signed-off-by: Yury Norov <ynorov@marvell.com>
---
 include/linux/cpumask.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 147bdec42215..2b87f35c586c 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -633,8 +633,7 @@ static inline int cpumask_parselist_user(const char __user *buf, int len,
  */
 static inline int cpumask_parse(const char *buf, struct cpumask *dstp)
 {
-	char *nl = strchr(buf, '\n');
-	unsigned int len = nl ? (unsigned int)(nl - buf) : strlen(buf);
+	unsigned int len = (unsigned int)(strchrnul(buf, '\n') - buf);
 
 	return bitmap_parse(buf, len, cpumask_bits(dstp), nr_cpumask_bits);
 }
-- 
2.17.1

