This is a note to let you know that I've just added the patch titled

tracing: Remove extra zeroing out of the ring buffer page

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: tracing-remove-extra-zeroing-out-of-the-ring-buffer-page.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 6b7e633fe9c24682df550e5311f47fb524701586 Mon Sep 17 00:00:00 2001

From: "Steven Rostedt (VMware)" rostedt@goodmis.org Date: Fri, 22 Dec 2017 20:38:57 -0500 Subject: tracing: Remove extra zeroing out of the ring buffer page

From: Steven Rostedt (VMware) rostedt@goodmis.org

commit 6b7e633fe9c24682df550e5311f47fb524701586 upstream.

The ring_buffer_read_page() takes care of zeroing out any extra data in the page that it returns. There's no need to zero it out again from the consumer. It was removed from one consumer of this function, but read_buffers_splice_read() did not remove it, and worse, it contained a nasty bug because of it.

Fixes: 2711ca237a084 ("ring-buffer: Move zeroing out excess in page to ring buffer code") Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- kernel/trace/trace.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-)

--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6181,7 +6181,7 @@ tracing_buffers_splice_read(struct file .spd_release = buffer_spd_release, }; struct buffer_ref *ref; - int entries, size, i; + int entries, i; ssize_t ret = 0;

#ifdef CONFIG_TRACER_MAX_TRACE @@ -6232,14 +6232,6 @@ tracing_buffers_splice_read(struct file break; }

- /* - * zero out any left over data, this is going to - * user land. - */ - size = ring_buffer_page_len(ref->page); - if (size < PAGE_SIZE) - memset(ref->page + size, 0, PAGE_SIZE - size); - page = virt_to_page(ref->page);

spd.pages[i] = page;

Patches currently in stable-queue which might be from rostedt@goodmis.org are

queue-4.9/tracing-fix-crash-when-it-fails-to-alloc-ring-buffer.patch queue-4.9/tracing-remove-extra-zeroing-out-of-the-ring-buffer-page.patch queue-4.9/tracing-fix-possible-double-free-on-failure-of-allocating-trace-buffer.patch