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

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

(2015/03/04 19:01), He Kuang wrote:
> 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.

Good catch!

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Thank you,

> 
> Signed-off-by: He Kuang <hekuang@huawei.com>
> ---
>  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;
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com