Re: [PATCH] tracing: eprobe: read the complete FILTER_PTR_STRING pointer

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Fri, 26 Jun 2026 06:42:23 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 26 Jun 2026 12:20:36 +0200
> Martin Kaiser <martin@kaiser.cx> wrote:
> 
> > > That is, to have +u0() say "this is going to be dereferencing user space".  
> > 
> > > I'll add Martin's patch and see if it makes the above work.  
> > 
> > I've just tried your command with my patch. It works for me, filenames are
> > logged correctly.
> 
> Yep, this definitely looks like a fix. We have;
> 
> 	addr = rec + field->offset;
> 
> Where addr points to the location of the field on the ring buffer, thus
> your change to make it:
> 
> 	val = *(unsigned long *)addr;
> 
> Reads the full "long size" of the event on the ring buffer, instead of
> reading just one byte. It is "val" that gets dereferenced later by the
> probe logic (the "+0u()"), which has all the protections we need.
> 
> I'll queue this up.

I've already queued this on my probes/core branch.
(which will be probes/fixes)

Thanks,

> 
> Thanks!
> 
> -- Steve


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>