Re: [PATCH 0/5] kallsyms: make kallsym APIs more safe with scnprintf

[Petr Mladek <pmladek@suse.com>]

On Mon 2022-05-23 12:39:12, Kees Cook wrote:
> On Sat, May 21, 2022 at 11:07:52PM -0700, Christoph Hellwig wrote:
> > On Fri, May 20, 2022 at 02:06:56PM +0530, Maninder Singh wrote:
> > > kallsyms functionality depends on KSYM_NAME_LEN directly.
> > > but if user passed array length lesser than it, sprintf
> > > can cause issues of buffer overflow attack.
> > > 
> > > So changing *sprint* and *lookup* APIs in this patch set
> > > to have buffer size as an argument and replacing sprintf with
> > > scnprintf.
> > 
> > This is still a pretty horrible API.  Passing something like
> > a struct seq_buf seems like the much better API here.  Also with
> > the amount of arguments and by reference passing it might be worth
> > to pass them as a structure while you're at it.
> 
> Yeah, I agree. It really seems like seq_buf would be nicer.

There is a new patchset that is trying to use this kind of buffer
in vsprintf.

It introduces another buffer struct because vsprintf() needs a bit
different semantic than the one used in seq_buf. But it actually
replaces seq_buf() in the end. I am not sure if this is the right
approach.

Anyway, the initial API is very simple, see
https://lore.kernel.org/r/20220604193042.1674951-2-kent.overstreet@gmail.com

And it makes the internal vsprintf() API more sane, see
https://lore.kernel.org/r/20220604193042.1674951-4-kent.overstreet@gmail.com

It would eventually solve also concerns about the kallsysms API.
Any comments on the new printbuf API are much appreaciated.

Best Regards,
Petr