Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH 3.12 20/84] tracing: Move mutex to protect against resetting of seq data | Date | Mon, 17 Oct 2016 09:51:07 +0200 |
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From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
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: Jiri Slaby <jslaby@suse.cz> --- kernel/trace/trace.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 140f4d6e6caa..174b9a6feea3 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4132,13 +4132,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, struct trace_array *tr = iter->tr; 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); - /* copy the tracer to avoid using a global lock all around */ mutex_lock(&trace_types_lock); if (unlikely(iter->trace->name != tr->current_trace->name)) @@ -4151,6 +4144,14 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, * 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) -- 2.10.1
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