Messages in this thread | | | From | Rickard Strandqvist <> | Date | Thu, 16 Oct 2014 19:41:55 +0200 | Subject | Re: [PATCH 3v] char: hw_random: core.c: Changed from using strncat to strlcat |
| |
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. >
Hi Joe
Yes that did not take advantage last strlcat was foolish.
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.
Kind regards Rickard Strandqvist
| |