perf: Disable monitoring on setuid processes for regular users

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@google.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/exec.c b/fs/exec.c
index 312e297..a2d0e51 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1159,13 +1159,6 @@ void setup_new_exec(struct linux_binprm * bprm)
                        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_binprm *bprm)
 
        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