linux-kernel - [PATCH] cpumask: fix double string traverse in cpumask

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Message-Id: <20190409204208.12190-1-ynorov@marvell.com>
Date:   Tue,  9 Apr 2019 13:42:08 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        "David S. Miller" <davem@...emloft.net>, Tejun Heo <tj@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>
Cc:     Yury Norov <ynorov@...vell.com>, Yury Norov <yury.norov@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] cpumask: fix double string traverse in cpumask_parse

From: Yury Norov <ynorov@...vell.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@...vell.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