Messages in this thread | | | Date | Wed, 28 Sep 2022 18:39:45 +0300 | From | Andy Shevchenko <> | Subject | Re: [PATCH v2 3/4] pwm: sysfs: Replace sprintf() with sysfs_emit() |
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On Wed, Sep 28, 2022 at 05:20:07PM +0200, Thierry Reding wrote: > On Wed, Sep 28, 2022 at 04:58:17PM +0300, Andy Shevchenko wrote: > > On Wed, Sep 28, 2022 at 04:40:35PM +0300, Andy Shevchenko wrote: > > > On Wed, Sep 28, 2022 at 02:28:41PM +0200, Thierry Reding wrote: > > > > On Fri, Aug 26, 2022 at 08:07:15PM +0300, Andy Shevchenko wrote: > > > > > For sysfs outputs, it's safer to use a new helper, sysfs_emit(), > > > > > instead of the raw sprintf() & co. This patch replaces such a > > > > > sprintf() call straightforwardly with the new helper. > > > > > > > How exactly is sysfs_emit() safer here? In all of these cases, the > > > > values that sprintf() writes are the only values that are written into > > > > the buffer and we know that none of them exceed PAGE_SIZE. So the > > > > additional checks that sysfs_emit() performs are useless. > > > > > > This is a recommended way to use sysfs_emit() mentioned in Documentation. > > > Care to fix documentation? > > > > For your convenience, Documentation/filesystems/sysfs.rst says: > > > > - show() should only use sysfs_emit() or sysfs_emit_at() when formatting > > the value to be returned to user space. > > Took some digging to find enough information to convince me. Again, the > commit message says that sysfs_emit() is safer, but that's a bad reason > in this case because these cases are fine. The sprintf() calls that this > replaces aren't unbound and we're not appending to an existing seq_buf, > so nothing to worry on that front. > > I think the better argument for broadly applying this is to specifically > distinguish the sysfs sprintf() calls from others so that they can be > auditioned better and perhaps help with the documentation[0]. > > Do you mind if I apply this with a reworded documentation?
I do not mind, go ahead with it. Thank you!
> Thierry > > [0]: https://lore.kernel.org/all/20200930115740.GA1611809@kroah.com/
-- With Best Regards, Andy Shevchenko
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