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Subject[PATCH] tracing: fix the "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>
---
fs/exec.c | 7 ++++---
include/trace/events/sched.h | 2 +-
2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index e48c66e..91db3e8 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1372,7 +1372,7 @@ 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)
@@ -1383,8 +1383,9 @@ 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;
@@ -1407,7 +1408,7 @@ 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 e61ddfe..2f10e81 100644
--- 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),
--
1.5.5.1



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