From: Jiri Olsa <jolsa@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Jiri Olsa <jolsa@redhat.com>,
Corey Ashford <cjashfor@linux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@elte.hu>, Namhyung Kim <namhyung@kernel.org>,
Paul Mackerras <paulus@samba.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: [PATCHv2] perf: Fix vmalloc ring buffer free function
Date: Fri, 1 Mar 2013 17:34:49 +0100 [thread overview]
Message-ID: <1362155689-13719-1-git-send-email-jolsa@redhat.com> (raw)
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 <jstancek@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
---
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 */
+}
struct page *
perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
{
- if (pgoff > (1UL << page_order(rb)))
+ if (pgoff > page_nr(rb))
return NULL;
return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
@@ -336,10 +347,10 @@ 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);
+ nr = page_nr(rb);
base = rb->user_page;
- for (i = 0; i < nr + 1; i++)
+ for (i = 0; i < nr; i++)
perf_mmap_unmark_page(base + (i * PAGE_SIZE));
vfree(base);
@@ -371,9 +382,24 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
goto fail_all_buf;
rb->user_page = all_buf;
- rb->data_pages[0] = all_buf + PAGE_SIZE;
- rb->page_order = ilog2(nr_pages);
- rb->nr_pages = 1;
+
+ /*
+ * For special case nr_pages == 0 we have
+ * only the user page mmaped plus:
+ *
+ * rb->data_pages[0] = NULL
+ * rb->nr_pages = 0
+ * rb->page_order = -1
+ *
+ * The perf_output_begin function is guarded
+ * by (rb->nr_pages > 0) condition, so no
+ * output code touches above setup if we
+ * have only user page allocated.
+ */
+
+ rb->data_pages[0] = nr_pages ? all_buf + PAGE_SIZE : NULL;
+ rb->nr_pages = nr_pages ? 1 : 0;
+ rb->page_order = ilog2(nr_pages);
ring_buffer_init(rb, watermark, flags);
--
1.7.11.7
next reply other threads:[~2013-03-01 16:35 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-01 16:34 Jiri Olsa [this message]
2013-03-06 14:30 ` [tip:perf/urgent] perf: Fix vmalloc ring buffer free function tip-bot for Jiri Olsa
2013-03-06 15:20 ` [PATCHv2] " Frederic Weisbecker
2013-03-06 15:37 ` Jiri Olsa
2013-03-06 15:40 ` Frederic Weisbecker
2013-03-11 9:40 ` Peter Zijlstra
2013-03-11 11:21 ` Jiri Olsa
2013-03-11 12:15 ` Ingo Molnar
2013-03-11 16:26 ` Peter Zijlstra
2013-03-11 16:43 ` Jiri Olsa
2013-03-11 17:44 ` Peter Zijlstra
2013-03-11 18:02 ` Jiri Olsa
2013-03-12 10:05 ` [PATCHv3] " Jiri Olsa
2013-03-12 10:27 ` Peter Zijlstra
2013-03-12 10:53 ` Jiri Olsa
2013-03-12 12:38 ` Peter Zijlstra
2013-03-12 13:52 ` Jiri Olsa
2013-03-12 15:26 ` Peter Zijlstra
2013-03-12 15:36 ` Jiri Olsa
2013-03-12 16:24 ` Peter Zijlstra
2013-03-12 17:04 ` Jiri Olsa
2013-03-13 11:15 ` Jiri Olsa
2013-03-18 19:05 ` Jiri Olsa
2013-03-19 11:46 ` Peter Zijlstra
2013-03-19 14:35 ` [PATCHv4] perf: Fix vmalloc ring buffer pages handling Jiri Olsa
2013-04-30 15:36 ` Jiri Olsa
2013-05-01 10:34 ` Ingo Molnar
2013-05-02 7:54 ` [tip:perf/urgent] " tip-bot for Jiri Olsa
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