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SubjectRe: [RFC][PATCH] tracing: Have traceprobe_probes_write() not access userspace unnecessarily
On Fri, 10 Feb 2017 08:53:02 +0100
Ingo Molnar <mingo@kernel.org> wrote:

>
> * Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > On Thu, 9 Feb 2017 18:04:58 -0500
> > Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > >
> > > The code in traceprobe_probes_write() reads up to 4096 bytes from userpace
> > > for each line. If userspace passes in several lines to execute, the code
> > > will do a large read for each line, even though, it is highly likely that
> > > the first read from userspace received all of the lines at one.
> > >
> > > I changed the logic to do a single read from userspace, and to only read
> > > from userspace again if not all of the read from userspace made it in.
> > >
> > > I tested this by adding printk()s and writing files that would test -1, ==,
> > > and +1 the buffer size, to make sure that there's no overflows and that if a
> > > single line is written with +1 the buffer size, that it fails properly.
> > >
> >
> > Thanks Steve!
> >
> > Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> >
> > BTW, this can conflict with my previous patch.
> >
> > https://lkml.org/lkml/2017/2/6/1048
> > https://lkml.org/lkml/2017/2/7/203
> >
> > I'll update this. Ingo, Can I send these patch to Steve?
>
> Sure, I've not applied your patch yet - mind sending it to Steve on top of Steve's
> patch?

Of course, yes. :)

Thanks!

>
> Thanks,
>
> Ingo


--
Masami Hiramatsu <mhiramat@kernel.org>

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