perf: Disable monitoring on setuid processes for regular users

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>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 9 insertions, 7 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 643019585574..ffd7a813ad3d 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1135,13 +1135,6 @@ 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 */
 
@@ -1205,6 +1198,15 @@ 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