Commit 5919b309 authored Mar 19, 2013 by Jiri Olsa Committed by Ingo Molnar May 01, 2013

perf: Fix vmalloc ring buffer pages handling



If we allocate perf ring buffer with the size of single (user)
page, we will get memory corruption when releasing itin
rb_free_work function (for 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.

Adding data_page_nr function that returns number of allocated
data pages. Customizing the rest of the code to use it.

Reported-by: Jan Stancek <jstancek@redhat.com>
Original-patch-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20130319143509.GA1128@krava.brq.redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 1b0dac2a

kernel/events/ring_buffer.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -326,11 +326,16 @@ void rb_free(struct ring_buffer *rb)
		}

		#else
		static int data_page_nr(struct ring_buffer *rb)
		{
		return rb->nr_pages << page_order(rb);
		}

		struct page *
		perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
		{
		if (pgoff > (1UL << page_order(rb)))
		/* The '>' counts in the user page. */
		if (pgoff > data_page_nr(rb))
		return NULL;

		return vmalloc_to_page((void )rb->user_page + pgoff PAGE_SIZE);
		@@ -350,10 +355,11 @@ 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 = data_page_nr(rb);

		base = rb->user_page;
		for (i = 0; i < nr + 1; i++)
		/* The '<=' counts in the user page. */
		for (i = 0; i <= nr; i++)
		perf_mmap_unmark_page(base + (i * PAGE_SIZE));

		vfree(base);
		@@ -387,7 +393,7 @@ struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
		rb->user_page = all_buf;
		rb->data_pages[0] = all_buf + PAGE_SIZE;
		rb->page_order = ilog2(nr_pages);
		rb->nr_pages = 1;
		rb->nr_pages = !!nr_pages;

		ring_buffer_init(rb, watermark, flags);

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