lkml.org 
[lkml]   [2014]   [Oct]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 3v] char: hw_random: core.c: Changed from using strncat to strlcat
From
Date
On Thu, 2014-10-16 at 19:41 +0200, Rickard Strandqvist wrote:
> 2014-10-16 19:25 GMT+02:00 Joe Perches <joe@perches.com>:
> > On Thu, 2014-10-16 at 19:15 +0200, Rickard Strandqvist wrote:
> >> The buf is used to hold the list of hwrng devices registered.
> >> The old code ensures we don't walk off the end of buf as we
> >> fill it, but it's unnecessarily complicated and thus difficult
> >> to maintain. Simplify it by using strlcat.
> >> We also ensure the string within buf is NULL terminated
> >> so the final strlen is ok.
> > []
> >> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> > []
> >> @@ -289,16 +288,13 @@ static ssize_t hwrng_attr_available_show(struct device *dev,
> >> return -ERESTARTSYS;
> >> buf[0] = '\0';
> >> list_for_each_entry(rng, &rng_list, list) {
> >> - strncat(buf, rng->name, PAGE_SIZE - ret - 1);
> >> - ret += strlen(rng->name);
> >> - strncat(buf, " ", PAGE_SIZE - ret - 1);
> >> - ret++;
> >> + strlcat(buf, rng->name, PAGE_SIZE);
> >> + strlcat(buf, " ", PAGE_SIZE);
> >> }
> >> - strncat(buf, "\n", PAGE_SIZE - ret - 1);
> >> - ret++;
> >> + strlcat(buf, "\n", PAGE_SIZE);
> >> mutex_unlock(&rng_mutex);
> >>
> >> - return ret;
> >> + return strlen(buf);
> >> }
> >>
> >> static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
> >
> > Rickard, can you please use some optimizations here
> > (and elsewhere) so that strlcat doesn't always have
> > to strlen the first string and the return doesn't
> > have to do the strlen too?
> >
> > You could use a temporary for the returned length
> > of the strlcat so that if it's shorter than
> > the buffer, the next strlcat can start at the
> > appropriate known position instead of having
> > to do the initial strlen again and again.
[]
> But the others, I am very hesitant about. Because strlcat like
> snprintf and strlcpy returns the length that would be copied rather
> than what is actually copied. Hence such a code to be even more
> complex than before.

None of the conversions you've done seem to use the
return value so maybe there should be yet another
function that doesn't return an overrun value.




\
 
 \ /
  Last update: 2014-10-16 20:21    [W:0.038 / U:0.152 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site