linux-kernel - [42/85] perf: Disable monitoring on setuid processes for regular users

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Date:	Wed, 24 Jul 2013 15:02:45 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Ingo Molnar" <mingo@...nel.org>,
	"Stephane Eranian" <eranian@...gle.com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Jiri Olsa" <jolsa@...hat.com>
Subject: [42/85] perf: Disable monitoring on setuid processes for regular
 users

3.2.49-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Stephane Eranian <eranian@...gle.com>

commit 2976b10f05bd7f6dab9f9e7524451ddfed656a89 upstream.

There was a a bug in setup_new_exec(), whereby
the test to disabled perf monitoring was not
correct because the new credentials for the
process were not yet committed and therefore
the get_dumpable() test was never firing.

The patch fixes the problem by moving the
perf_event test until after the credentials
are committed.

Signed-off-by: Stephane Eranian <eranian@...gle.com>
Tested-by: Jiri Olsa <jolsa@...hat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/exec.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1159,13 +1159,6 @@ void setup_new_exec(struct linux_binprm
 			set_dumpable(current->mm, suid_dumpable);
 	}
 
-	/*
-	 * Flush performance counters when crossing a
-	 * security domain:
-	 */
-	if (!get_dumpable(current->mm))
-		perf_event_exit_task(current);
-
 	/* An exec changes our domain. We are no longer part of the thread
 	   group */
 
@@ -1229,6 +1222,15 @@ void install_exec_creds(struct linux_bin
 
 	commit_creds(bprm->cred);
 	bprm->cred = NULL;
+
+	/*
+	 * Disable monitoring for regular users
+	 * when executing setuid binaries. Must
+	 * wait until new credentials are committed
+	 * by commit_creds() above
+	 */
+	if (get_dumpable(current->mm) != SUID_DUMP_USER)
+		perf_event_exit_task(current);
 	/*
 	 * cred_guard_mutex must be held at least to this point to prevent
 	 * ptrace_attach() from altering our determination of the task's

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