diff options
| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2016-09-23 22:57:13 -0400 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2016-09-25 10:27:08 -0400 |
| commit | 1245800c0f96eb6ebb368593e251d66c01e61022 (patch) | |
| tree | c945fb377258b480d806786d33fbd0f6ce118022 | |
| parent | c87edb36118664f1fa275107c1138b6f47793240 (diff) | |
| download | linux-1245800c0f96eb6ebb368593e251d66c01e61022.tar.bz2 | |
tracing: Move mutex to protect against resetting of seq data
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")
Cc: stable@vger.kernel.org # 2.6.30+
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/trace.c | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 8a4bd6b68a0b..8fb4847b0450 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4890,19 +4890,20 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, 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) |