linux-kernel - Re: [PATCH v2] perf/core: use strndup_user() instead of buggy open-coded version

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Date:   Thu, 21 Feb 2019 10:33:03 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Song Liu <songliubraving@...com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Jann Horn <jannh@...gle.com>, Ingo Molnar <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] perf/core: use strndup_user() instead of buggy
 open-coded version

On Thu, 21 Feb 2019 07:12:10 +0000
Song Liu <songliubraving@...com> wrote:

> > On Feb 20, 2019, at 4:20 PM, Masami Hiramatsu <mhiramat@...nel.org> wrote:
> > 
> > Hi Jann,
> > 
> > On Wed, 20 Feb 2019 17:54:43 +0100
> > Jann Horn <jannh@...gle.com> wrote:
> >   
> >> The first version of this method was missing the check for
> >> `ret == PATH_MAX`; then such a check was added, but it didn't call kfree()
> >> on error, so there was still a small memory leak in the error case.
> >> Fix it by using strndup_user() instead of open-coding it.
> >>   
> > 
> > This looks good to me.
> > 
> > Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
> > 
> > BTW, for stable, this is good. For the long term, I think we should
> > fix strndup_user() to return -E2BUG when the user string is longer
> > than max.

OK, I'll add a stable tag (but it wont go until the merge window).

It also shouldn't be called "perf/core" as its in the tracing
directory, and thus "tracing/perf" would be more appropriate. But I see
that's what the patch it fixes calls it too :-/

I'll pull it in.

Thanks everyone!

-- Steve


> > 
> > Thank you,
> >   
> >> Fixes: 0eadcc7a7bc0 ("perf/core: Fix perf_uprobe_init()")
> >> Signed-off-by: Jann Horn <jannh@...gle.com>  
> 
> Thanks for the fix!
> 
> Acked-by: Song Liu <songliubraving@...com>