4.14-stable review patch. If anyone has any objections, please let me know.
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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 @@ -6769,7 +6769,7 @@ 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 @@ -6823,14 +6823,6 @@ 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;