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* [PATCH] perf tools: Fix mode setting in copyfile_mode_ns()
@ 2019-10-07  7:02 Adrian Hunter
  2019-10-07 10:47 ` Jiri Olsa
  2019-10-21  6:26 ` [tip: perf/urgent] " tip-bot2 for Adrian Hunter
  0 siblings, 2 replies; 4+ messages in thread
From: Adrian Hunter @ 2019-10-07  7:02 UTC (permalink / raw)
  To: Arnaldo Carvalho de Melo, Jiri Olsa; +Cc: linux-kernel

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@intel.com>
---
 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


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2019-10-07  7:02 [PATCH] perf tools: Fix mode setting in copyfile_mode_ns() Adrian Hunter
2019-10-07 10:47 ` Jiri Olsa
2019-10-15 15:07   ` Arnaldo Carvalho de Melo
2019-10-21  6:26 ` [tip: perf/urgent] " tip-bot2 for Adrian Hunter

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