Currently only the tracing thread can call ptrace on a given pid. This
patch allows any task in the tracing thread's thread group to also call
ptrace. This makes it easier and more performant to write multi-threaded
applications that use ptrace.
In our ptrace-based simulator, we currently work-around this limitation
by stopping and detaching inactive tracees, so that any thread in our
worker thread pool can later re-attach and resume control of the tracee.
This detaching and reattaching carries with it a significant performance
overhead. With this patch, detaching and reattaching is no longer
necessary.
Signed-off-by: James Newsome <jnews...@torproject.org>
---
kernel/ptrace.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 821cf1723814..bd9968a35784 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -50,7 +50,7 @@ int ptrace_access_vm(struct task_struct *tsk, unsigned long
addr,
return 0;
if (!tsk->ptrace ||
- (current != tsk->parent) ||
+ !same_thread_group(current, tsk->parent) ||
((get_dumpable(mm) != SUID_DUMP_USER) &&
!ptracer_capable(tsk, mm->user_ns))) {
mmput(mm);
@@ -193,7 +193,7 @@ static void ptrace_unfreeze_traced(struct task_struct *task)
if (task->state != __TASK_TRACED)
return;
- WARN_ON(!task->ptrace || task->parent != current);
+ WARN_ON(!task->ptrace || !same_thread_group(task->parent, current));
/*
* PTRACE_LISTEN can allow ptrace_trap_notify to wake us up remotely.
@@ -238,7 +238,7 @@ static int ptrace_check_attach(struct task_struct *child,
bool ignore_state)
* be changed by us so it's not changing right after this.
*/
read_lock(&tasklist_lock);
- if (child->ptrace && child->parent == current) {
+ if (child->ptrace && same_thread_group(child->parent, current)) {
WARN_ON(child->state == __TASK_TRACED);
/*
* child->sighand can't be NULL, release_task()
--
2.30.1
