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SubjectRe: [PATCH] cpumask: fix double string traverse in cpumask_parse
On Tue, Apr 09, 2019 at 11:31:50PM +0200, Rasmus Villemoes wrote:
> On 09/04/2019 22.42, Yury Norov wrote:
> > 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);
>
> ack, but please drop the cast. "len = strchrnul(buf, '\n') - buf;"

Indeed. See below.

Thanks,
Yury

Subject: [PATCH] cpumask: fix double string traverse in cpumask_parse

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>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
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 = strchrnul(buf, '\n') - buf;

return bitmap_parse(buf, len, cpumask_bits(dstp), nr_cpumask_bits);
}
--
2.17.1
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