tracing, sched, vfs: Fix 'old_pid' usage in trace_sched_process_exec()

1. TRACE_EVENT(sched_process_exec) forgets to actually use the
   old pid argument, it sets ->old_pid = p->pid.

2. search_binary_handler() uses the wrong pid number. tracepoint
   needs the global pid_t from the root namespace, while old_pid
   is the virtual pid number as it seen by the tracer/parent.

With this patch we have two pid_t's in search_binary_handler(),
not really nice. Perhaps we should switch to "struct pid*", but
in this case it would be better to cleanup the current code
first and move the "depth == 0" code outside.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: David Smith <dsmith@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Link: http://lkml.kernel.org/r/20120330162636.GA4857@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/exec.c b/fs/exec.c
index 23559c227d9c..644f6c4eb606 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1370,7 +1370,7 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
         unsigned int depth = bprm->recursion_depth;
         int try,retval;
         struct linux_binfmt *fmt;
-        pid_t old_pid;
+        pid_t old_pid, old_vpid;
 
         retval = security_bprm_check(bprm);
         if (retval)
@@ -1381,8 +1381,9 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
                 return retval;
 
         /* Need to fetch pid before load_binary changes it */
+        old_pid = current->pid;
         rcu_read_lock();
-        old_pid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
+        old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
         rcu_read_unlock();
 
         retval = -ENOENT;
@@ -1405,7 +1406,7 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
                         if (retval >= 0) {
                                 if (depth == 0) {
                                         trace_sched_process_exec(current, old_pid, bprm);
-                                        ptrace_event(PTRACE_EVENT_EXEC, old_pid);
+                                        ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
                                 }
                                 put_binfmt(fmt);
                                 allow_write_access(bprm->file);