Patch "tracing: Fix crash from reading trace_pipe with sendfile" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    tracing: Fix crash from reading trace_pipe with sendfile

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tracing-fix-crash-from-reading-trace_pipe-with-sendfile.patch
and it can be found in the queue-4.4 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 a29054d9478d0435ab01b7544da4f674ab13f533 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
Date: Fri, 18 Mar 2016 15:46:48 -0400
Subject: tracing: Fix crash from reading trace_pipe with sendfile

From: Steven Rostedt (Red Hat) <rostedt@goodmis.org>

commit a29054d9478d0435ab01b7544da4f674ab13f533 upstream.

If tracing contains data and the trace_pipe file is read with sendfile(),
then it can trigger a NULL pointer dereference and various BUG_ON within the
VM code.

There's a patch to fix this in the splice_to_pipe() code, but it's also a
good idea to not let that happen from trace_pipe either.

Link: http://lkml.kernel.org/r/1457641146-9068-1-git-send-email-rabin@rab.in

Reported-by: Rabin Vincent <rabin.vincent@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/trace/trace.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4949,7 +4949,10 @@ static ssize_t tracing_splice_read_pipe(
 
 	spd.nr_pages = i;
 
-	ret = splice_to_pipe(pipe, &spd);
+	if (i)
+		ret = splice_to_pipe(pipe, &spd);
+	else
+		ret = 0;
 out:
 	splice_shrink_spd(&spd);
 	return ret;


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

queue-4.4/tracing-fix-trace_printk-to-print-when-not-using-bprintk.patch
queue-4.4/tracing-fix-crash-from-reading-trace_pipe-with-sendfile.patch
queue-4.4/tracing-have-preempt-irqs-off-trace-preempt-disabled-functions.patch