From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
This patch has been added to the 4.1 stable tree. If you have any
objections, please let us know.
===============
[ Upstream commit 6b7e633fe9c24682df550e5311f47fb524701586 ]
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.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 2711ca237a084 ("ring-buffer: Move zeroing out excess in page to ring buffer code")
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
---
kernel/trace/trace.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7a26798ffbf9..915fffdc5329 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5719,7 +5719,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
.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
@@ -5770,14 +5770,6 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
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;
--
2.14.1