Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758348Ab3CFPUW (ORCPT ); Wed, 6 Mar 2013 10:20:22 -0500 Received: from mail-la0-f52.google.com ([209.85.215.52]:54478 "EHLO mail-la0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757481Ab3CFPUS (ORCPT ); Wed, 6 Mar 2013 10:20:18 -0500 MIME-Version: 1.0 In-Reply-To: <1362155689-13719-1-git-send-email-jolsa@redhat.com> References: <1362155689-13719-1-git-send-email-jolsa@redhat.com> Date: Wed, 6 Mar 2013 16:20:15 +0100 Message-ID: Subject: Re: [PATCHv2] perf: Fix vmalloc ring buffer free function From: Frederic Weisbecker To: Jiri Olsa Cc: linux-kernel@vger.kernel.org, Corey Ashford , Ingo Molnar , Namhyung Kim , Paul Mackerras , Peter Zijlstra , Arnaldo Carvalho de Melo Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2826 Lines: 70 2013/3/1 Jiri Olsa : > 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 (CONFIG_PERF_USE_VMALLOC option). > > 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 to release proper amount of pages. > > Introducing page_nr function (CONFIG_PERF_USE_VMALLOC only) > that returns number of allocated pages. Using it in rb_free_work > and perf_mmap_to_page functions. > > Also setting rb->nr_pages to 0 in case we have only user page > allocated, which will fail perf_output_begin function and > prevents sample storage. > > v2 changes: > - fixed the perf_output_begin handling of single page buffer > > Reported-by: Jan Stancek > Signed-off-by: Jiri Olsa > Cc: Corey Ashford > Cc: Frederic Weisbecker > Cc: Ingo Molnar > Cc: Namhyung Kim > Cc: Paul Mackerras > Cc: Peter Zijlstra > Cc: Arnaldo Carvalho de Melo > --- > kernel/events/ring_buffer.c | 40 +++++++++++++++++++++++++++++++++------- > 1 file changed, 33 insertions(+), 7 deletions(-) > > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c > index 23cb34f..a802151 100644 > --- a/kernel/events/ring_buffer.c > +++ b/kernel/events/ring_buffer.c > @@ -154,7 +154,8 @@ int perf_output_begin(struct perf_output_handle *handle, > if (head - local_read(&rb->wakeup) > rb->watermark) > local_add(rb->watermark, &rb->wakeup); > > - handle->page = offset >> (PAGE_SHIFT + page_order(rb)); > + /* page is allways 0 for CONFIG_PERF_USE_VMALLOC option */ > + handle->page = offset >> PAGE_SHIFT; > handle->page &= rb->nr_pages - 1; > handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1); > handle->addr = rb->data_pages[handle->page]; > @@ -312,11 +313,21 @@ void rb_free(struct ring_buffer *rb) > } > > #else > +/* > + * Returns the total number of pages allocated > + * by ring buffer including the user page. > + */ > +static int page_nr(struct ring_buffer *rb) > +{ > + return page_order(rb) == -1 ? > + 1 : /* no data, just user page */ > + 1 + (1 << page_order(rb)); /* user page + data pages */ > +} Could be simply rb->nr_page + 1 ? Patch looks good in any case. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/