On Wed, Feb 27, 2013 at 02:02:39PM +0100, Frederic Weisbecker wrote: > 2013/2/26 Jiri Olsa <[email protected]>: > > If we allocate perf ring buffer with the size of single page, > > we will get memory corruption when releasing it. It's caused > > by rb_free_work function (the CONFIG_PERF_USE_VMALLOC option > > variant). > > > > For single page sized ring buffer the page_order is -1 (because > > nr_pages is 0). This needs to be recognized in the rb_free_work > > function and set 'nr' to 0 in this case, so only the user page > > gets freed. > > > > Reported-by: Jan Stancek <[email protected]> > > Signed-off-by: Jiri Olsa <[email protected]> > > Cc: Corey Ashford <[email protected]> > > Cc: Frederic Weisbecker <[email protected]> > > Cc: Ingo Molnar <[email protected]> > > Cc: Namhyung Kim <[email protected]> > > Cc: Paul Mackerras <[email protected]> > > Cc: Peter Zijlstra <[email protected]> > > Cc: Arnaldo Carvalho de Melo <[email protected]> > > --- > > kernel/events/ring_buffer.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c > > index 23cb34f..21159fb 100644 > > --- a/kernel/events/ring_buffer.c > > +++ b/kernel/events/ring_buffer.c > > @@ -336,7 +336,8 @@ static void rb_free_work(struct work_struct *work) > > int i, nr; > > > > rb = container_of(work, struct ring_buffer, work); > > - nr = 1 << page_order(rb); > > + /* -1 if there's only user page */ > > + nr = page_order(rb) == -1 ? 0 : 1 << page_order(rb); > > So we allow for 0 sized ring buffer? I'm not entirely convinced this > is a good idea. Besides this above case, perf_output_begin() looks
We actually have test perf case 'tools/perf/tests/rdpmc.c' using just the user page for counter id and other stuff.. > dangerous in the case of CONFIG_PERF_USE_VMALLOC due to page_order() > being -1. At least rb->nr_pages sould be zero in that case. right, seems to suffer the same way as rb_free_work.. will check thanks, jirka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
