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