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>

diff --git a/fs/exec.c b/fs/exec.c
index 23559c227d9cb4f9480855590df611999e852dd4..644f6c4eb606056b931fdaed3a0dc7ff8f5d712d 100644 (file)
--- 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);

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index fbc7b1ad929bd007940233e3e1bd9a4e9eb31829..ea7a2035456d4f913e15b9997696ab5ca4934ad1 100644 (file)
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -295,7 +295,7 @@ TRACE_EVENT(sched_process_exec,
        TP_fast_assign(
                __assign_str(filename, bprm->filename);
                __entry->pid            = p->pid;
-               __entry->old_pid        = p->pid;
+               __entry->old_pid        = old_pid;
        ),
 
        TP_printk("filename=%s pid=%d old_pid=%d", __get_str(filename),