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SubjectRe: [PATCH v2 1/3] tracing: uprobes: Re-enable $comm support for uprobe events
On Wed, 6 Feb 2019 15:52:43 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 18 Jan 2019 13:44:25 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > @@ -180,7 +183,12 @@ fetch_store_strlen(unsigned long addr)
> > int len;
> > void __user *vaddr = (void __force __user *) addr;
> >
> > - len = strnlen_user(vaddr, MAX_STRING_SIZE);
> > + if (addr == (unsigned long)current->comm) {
> > + len = strlen(current->comm);
> > + if (len)
> > + len++;
>
> Why only add 1 if len is non zero? Why not always do it.
>
> One thing, len should always be greater than 0, and the other is that
> this makes it inconsistent with the NULL case of reading the address in
> userspace.

Agreed, it should not 0, so it should be;
len = strlen(current->comm) + 1;

Thank you!

>
> -- Steve
>
>
> > + } else
> > + len = strnlen_user(vaddr, MAX_STRING_SIZE);
> >
> > return (len > MAX_STRING_SIZE) ? 0 : len;


--
Masami Hiramatsu <mhiramat@kernel.org>

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