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 <[email protected]>
> ---
>
> 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
