diff options
| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2016-09-23 22:57:13 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-09-30 10:18:38 +0200 |
| commit | 8b275b4522af2b19072df7aee87fd659e09d29bc (patch) | |
| tree | 550193c52da9e4d98746ca9066be780d0eb679d0 /kernel | |
| parent | 369796a8843ec9fce05129c6a80bee9e4b90978b (diff) | |
tracing: Move mutex to protect against resetting of seq data
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@ZenIV.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -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 3a44903169ec..059233abcfcf 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4727,19 +4727,20 @@ 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) |