[PATCH] perf tools: Fix possible double free on error

[He Kuang]

A double free occurred when get source file path failed. If lr->path
failed to assign a new value, it will be freed as the old path and then
be freed again during line_range__clear(), and causes this:

  $ perf probe -L do_execve -k vmlinux
  *** Error in `/usr/bin/perf': double free or corruption (fasttop):
      0x0000000000a9ac50 ***
  ======= Backtrace: =========
  ../lib64/libc.so.6(+0x6eeef)[0x7ffff5e44eef]
  ../lib64/libc.so.6(+0x78cae)[0x7ffff5e4ecae]
  ../lib64/libc.so.6(+0x79987)[0x7ffff5e4f987]
  ../bin/perf[0x4ab41f]
  ...

This patch fix this problem.

Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
---
 tools/perf/util/probe-event.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 919937e..7df30bd 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -650,7 +650,11 @@ static int __show_line_range(struct line_range *lr, const char *module)
 	/* Convert source file path */
 	tmp = lr->path;
 	ret = get_real_path(tmp, lr->comp_dir, &lr->path);
-	free(tmp);	/* Free old path */
+
+	/* Free old path when new path is assigned */
+	if (tmp != lr->path)
+		free(tmp);
+
 	if (ret < 0) {
 		pr_warning("Failed to find source file path.\n");
 		return ret;
-- 
2.2.0.33.gc18b867

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