[PATCH 4.9 008/144] tracing/kprobes: Fix trace_probe flags on enable_trace_kprobe() failure

From: Greg Kroah-Hartman
Date: Wed Aug 01 2018 - 13:25:26 EST


4.9-stable review patch. If anyone has any objections, please let me know.

------------------

From: Artem Savkov <asavkov@xxxxxxxxxx>

commit 57ea2a34adf40f3a6e88409aafcf803b8945619a upstream.

If enable_trace_kprobe fails to enable the probe in enable_k(ret)probe
it returns an error, but does not unset the tp flags it set previously.
This results in a probe being considered enabled and failures like being
unable to remove the probe through kprobe_events file since probes_open()
expects every probe to be disabled.

Link: http://lkml.kernel.org/r/20180725102826.8300-1-asavkov@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20180725142038.4765-1-asavkov@xxxxxxxxxx

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 41a7dd420c57 ("tracing/kprobes: Support ftrace_event_file base multibuffer")
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
kernel/trace/trace_kprobe.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)

--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -359,11 +359,10 @@ static struct trace_kprobe *find_trace_k
static int
enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
{
+ struct event_file_link *link;
int ret = 0;

if (file) {
- struct event_file_link *link;
-
link = kmalloc(sizeof(*link), GFP_KERNEL);
if (!link) {
ret = -ENOMEM;
@@ -383,6 +382,16 @@ enable_trace_kprobe(struct trace_kprobe
else
ret = enable_kprobe(&tk->rp.kp);
}
+
+ if (ret) {
+ if (file) {
+ list_del_rcu(&link->list);
+ kfree(link);
+ tk->tp.flags &= ~TP_FLAG_TRACE;
+ } else {
+ tk->tp.flags &= ~TP_FLAG_PROFILE;
+ }
+ }
out:
return ret;
}