linux-kernel - Re: Suspected SPAM - Re: [PATCH 4.14 198/205] perf/core: Dont WARN() for impossible ring-buffer sizes

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Date:   Wed, 13 Feb 2019 13:10:52 +0000
From:   "Rantala, Tommi T. (Nokia - FI/Espoo)" <tommi.t.rantala@...ia.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "mingo@...nel.org" <mingo@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "jolsa@...hat.com" <jolsa@...hat.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "namhyung@...nel.org" <namhyung@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "acme@...hat.com" <acme@...hat.com>,
        "alexander.shishkin@...ux.intel.com" 
        <alexander.shishkin@...ux.intel.com>,
        "julien.thierry@....com" <julien.thierry@....com>
Subject: Re: Suspected SPAM - Re: [PATCH 4.14 198/205] perf/core: Dont WARN()
 for impossible ring-buffer sizes

On Wed, 2019-02-13 at 13:03 +0000, Rantala, Tommi T. (Nokia - FI/Espoo)
wrote:
> On Mon, 2019-02-11 at 15:19 +0100, Greg Kroah-Hartman wrote:
> > 4.14-stable review patch.  If anyone has any objections, please let
> > me know.
> > 
> > ------------------
> > 
> > From: Mark Rutland <mark.rutland@....com>
> > 
> > commit 9dff0aa95a324e262ffb03f425d00e4751f3294e upstream.
> > 
> > The perf tool uses /proc/sys/kernel/perf_event_mlock_kb to
> > determine
> > how
> > large its ringbuffer mmap should be. This can be configured to
> > arbitrary
> > values, which can be larger than the maximum possible allocation
> > from
> > kmalloc.
> > 
> > When this is configured to a suitably large value (e.g. thanks to
> > the
> > perf fuzzer), attempting to use perf record triggers a
> > WARN_ON_ONCE()
> > in
> > __alloc_pages_nodemask():
> > 
> >    WARNING: CPU: 2 PID: 5666 at mm/page_alloc.c:4511
> > __alloc_pages_nodemask+0x3f8/0xbc8
> > 
> > Let's avoid this by checking that the requested allocation is
> > possible
> > before calling kzalloc.
> 
> Hi,
> 
> Perf tool is broken for me in 4.14.99 (running in x86_64 VM),
> bisection
> points to this patch.

... and I see there's a fix available:

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=528871b456026e6127d95b1b2bd8e3a003dc1614

-Tommi

> 
> 
> > Reported-by: Julien Thierry <julien.thierry@....com>
> > Signed-off-by: Mark Rutland <mark.rutland@....com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > Reviewed-by: Julien Thierry <julien.thierry@....com>
> > Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> > Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Cc: Jiri Olsa <jolsa@...hat.com>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Namhyung Kim <namhyung@...nel.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: <stable@...r.kernel.org>
> > Link: 
> > https://lkml.kernel.org/r/20190110142745.25495-1-mark.rutland@arm.com
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > ---
> >  kernel/events/ring_buffer.c |    3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > --- a/kernel/events/ring_buffer.c
> > +++ b/kernel/events/ring_buffer.c
> > @@ -719,6 +719,9 @@ struct ring_buffer *rb_alloc(int nr_page
> >  	size = sizeof(struct ring_buffer);
> >  	size += nr_pages * sizeof(void *);
> >  
> > +	if (order_base_2(size) >= MAX_ORDER)
> > +		goto fail;
> > +
> >  	rb = kzalloc(size, GFP_KERNEL);
> >  	if (!rb)
> >  		goto fail;
> > 
> >