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Subject[for-next][PATCH 4/4] tracing/uprobes: Fix the usage of uprobe_buffer_enable() in probe_event_enable()
From: Oleg Nesterov <oleg@redhat.com>

The usage of uprobe_buffer_enable() added by dcad1a20 is very wrong,

1. uprobe_buffer_enable() and uprobe_buffer_disable() are not balanced,
_enable() should be called only if !enabled.

2. If uprobe_buffer_enable() fails probe_event_enable() should clear
tp.flags and free event_file_link.

3. If uprobe_register() fails it should do uprobe_buffer_disable().

Link: http://lkml.kernel.org/p/20140627170146.GA18332@redhat.com

Acked-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Fixes: dcad1a204f72 "tracing/uprobes: Fetch args before reserving a ring buffer"
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_uprobe.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index c4cf0abd60ba..3c9b97e6b1f4 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -911,26 +911,33 @@ probe_event_enable(struct trace_uprobe *tu, struct ftrace_event_file *file,
tu->tp.flags |= TP_FLAG_PROFILE;
}

- ret = uprobe_buffer_enable();
- if (ret < 0)
- return ret;
-
WARN_ON(!uprobe_filter_is_empty(&tu->filter));

if (enabled)
return 0;

+ ret = uprobe_buffer_enable();
+ if (ret)
+ goto err_flags;
+
tu->consumer.filter = filter;
ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
- if (ret) {
- if (file) {
- list_del(&link->list);
- kfree(link);
- tu->tp.flags &= ~TP_FLAG_TRACE;
- } else
- tu->tp.flags &= ~TP_FLAG_PROFILE;
- }
+ if (ret)
+ goto err_buffer;

+ return 0;
+
+ err_buffer:
+ uprobe_buffer_disable();
+
+ err_flags:
+ if (file) {
+ list_del(&link->list);
+ kfree(link);
+ tu->tp.flags &= ~TP_FLAG_TRACE;
+ } else {
+ tu->tp.flags &= ~TP_FLAG_PROFILE;
+ }
return ret;
}

--
2.0.0



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