This is a note to let you know that I've just added the patch titled
tracing: Move mutex to protect against resetting of seq data
to the 4.7-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-move-mutex-to-protect-against-resetting-of-seq-data.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1245800c0f96eb6ebb368593e251d66c01e61022 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
Date: Fri, 23 Sep 2016 22:57:13 -0400
Subject: tracing: Move mutex to protect against resetting of seq data
From: Steven Rostedt (Red Hat) <rostedt@xxxxxxxxxxx>
commit 1245800c0f96eb6ebb368593e251d66c01e61022 upstream.
The iter->seq can be reset outside the protection of the mutex. So can
reading of user data. Move the mutex up to the beginning of the function.
Fixes: d7350c3f45694 ("tracing/core: make the read callbacks reentrants")
Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4890,19 +4890,20 @@ tracing_read_pipe(struct file *filp, cha
struct trace_iterator *iter = filp->private_data;
ssize_t sret;
- /* return any leftover data */
- sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
- if (sret != -EBUSY)
- return sret;
-
- trace_seq_init(&iter->seq);
-
/*
* Avoid more than one consumer on a single file descriptor
* This is just a matter of traces coherency, the ring buffer itself
* is protected.
*/
mutex_lock(&iter->mutex);
+
+ /* return any leftover data */
+ sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
+ if (sret != -EBUSY)
+ goto out;
+
+ trace_seq_init(&iter->seq);
+
if (iter->trace->read) {
sret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
if (sret)
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-4.7/makefile-mute-warning-for-__builtin_return_address-0-for-tracing-only.patch
queue-4.7/disable-frame-address-warning.patch
queue-4.7/tracing-move-mutex-to-protect-against-resetting-of-seq-data.patch
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