Re: [PATCH] perf tools: Fix mode setting in copyfile_mode_ns()
From: Jiri Olsa
Date: Mon Oct 07 2019 - 06:47:50 EST
On Mon, Oct 07, 2019 at 10:02:21AM +0300, Adrian Hunter wrote:
> slow_copyfile() opens the file by name, so "write" permissions must not
> be removed in copyfile_mode_ns() before calling slow_copyfile().
>
> Example:
>
> Before:
> $ sudo chmod +r /proc/kcore
> $ sudo setcap "cap_sys_admin,cap_sys_ptrace,cap_syslog,cap_sys_rawio=ep" tools/perf/perf
> $ tools/perf/perf buildid-cache -k /proc/kcore
> Couldn't add /proc/kcore
>
> After:
> $ sudo chmod +r /proc/kcore
> $ sudo setcap "cap_sys_admin,cap_sys_ptrace,cap_syslog,cap_sys_rawio=ep" tools/perf/perf
> $ tools/perf/perf buildid-cache -v -k /proc/kcore
> kcore added to build-id cache directory /home/ahunter/.debug/[kernel.kcore]/37e340b1b5a7cf4f57ba8de2bc777359588a957f/2019100709562289
>
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
thanks,
jirka
> ---
> tools/perf/util/copyfile.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/copyfile.c b/tools/perf/util/copyfile.c
> index 3fa0db136667..47e03de7c235 100644
> --- a/tools/perf/util/copyfile.c
> +++ b/tools/perf/util/copyfile.c
> @@ -101,14 +101,16 @@ static int copyfile_mode_ns(const char *from, const char *to, mode_t mode,
> if (tofd < 0)
> goto out;
>
> - if (fchmod(tofd, mode))
> - goto out_close_to;
> -
> if (st.st_size == 0) { /* /proc? do it slowly... */
> err = slow_copyfile(from, tmp, nsi);
> + if (!err && fchmod(tofd, mode))
> + err = -1;
> goto out_close_to;
> }
>
> + if (fchmod(tofd, mode))
> + goto out_close_to;
> +
> nsinfo__mountns_enter(nsi, &nsc);
> fromfd = open(from, O_RDONLY);
> nsinfo__mountns_exit(&nsc);
> --
> 2.17.1
>