From: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
Date: Fri, 18 Mar 2016 19:46:48 +0000 (-0400)
Subject: tracing: Fix crash from reading trace_pipe with sendfile
X-Git-Tag: v4.1.12-92~150^2~30
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=1fac75f7a39b717dfd34992246cfcb3ef3b3f073;p=users%2Fjedix%2Flinux-maple.git

tracing: Fix crash from reading trace_pipe with sendfile

Orabug: 23331131

[ Upstream commit a29054d9478d0435ab01b7544da4f674ab13f533 ]

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

Cc: stable@vger.kernel.org # 2.6.30+
Reported-by: Rabin Vincent <rabin.vincent@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit ab31b690cdf88cf5cb0493718b89dbc37dd784a3)

Signed-off-by: Dan Duval <dan.duval@oracle.com>
---

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 05330494a0dff..de6ea94c41bb5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4916,7 +4916,10 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
 
 	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;