perf probe: Fix possible double free on error

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@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1425463302-1687-1-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 8af8e7f55254..e2bf620f98cb 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -790,7 +790,11 @@ 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;