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Message-ID: <lsq.1461711744.449454024@decadent.org.uk>
Date: Wed, 27 Apr 2016 01:02:24 +0200
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org,
"Rabin Vincent" <rabin.vincent@...il.com>,
"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
Subject: [PATCH 3.2 049/115] tracing: Fix crash from reading trace_pipe
with sendfile
3.2.80-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.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@...il.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
kernel/trace/trace.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3565,7 +3565,10 @@ 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;
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