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

Rantala, Tommi T. (Nokia - FI/Espoo)
2019-02-13T13:10:59Z

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@arm.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@arm.com>
> > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Reviewed-by: Julien Thierry <julien.thierry@arm.com>
> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> > Cc: Jiri Olsa <jolsa@redhat.com>
> > Cc: Linus Torvalds <torvalds@linux-foundation.org>
> > Cc: Namhyung Kim <namhyung@kernel.org>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: <stable@vger.kernel.org>
> > Link:
> > https://lkml.kernel.org/r/20190110142745.25495-1-mark.rutland@arm.com
> > Signed-off-by: Ingo Molnar <mingo@kernel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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;
> >
> >