Messages in this thread | | | Date | Sun, 21 Jun 2020 10:56:56 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] driver core: Use scnprintf() instead of snprintf() in device show functions |
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On Sat, Jun 20, 2020 at 06:05:29PM +0300, Denis Efremov wrote: > >From Documentation/filesystems/sysfs.txt: > - show() must not use snprintf() when formatting the value to be > returned to user space. If you can guarantee that an overflow > will never happen you can use sprintf() otherwise you must use > scnprintf(). > > The reason is that snprintf() returns the length the resulting string > would be, assuming the data will fit into the destination array. > scnprintf() returns the length of the string actually created in buf. > > device_show_{ulong,int,bool}() functions are reference implementation > and should respect the kernel documentation.
Ok, but you are not following that documentation below, why not?
> > Signed-off-by: Denis Efremov <efremov@linux.com> > --- > > Actually, I don't know why snprintf() is used here initially. It looks > safe to use sprintf(). > > drivers/base/core.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index 67d39a90b45c..2815deb511fc 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -1472,7 +1472,7 @@ ssize_t device_show_ulong(struct device *dev, > char *buf) > { > struct dev_ext_attribute *ea = to_ext_attr(attr); > - return snprintf(buf, PAGE_SIZE, "%lx\n", *(unsigned long *)(ea->var)); > + return scnprintf(buf, PAGE_SIZE, "%lx\n", *(unsigned long *)(ea->var));
As the documentation states, these should just be sprintf(), if you really want to change these.
As-is, these are also ok, there is no need to change.
thanks,
greg k-h
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