Commit 4576145c authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

ptrace: fix possible zombie leak on PTRACE_DETACH 



When ptrace_detach() takes tasklist, the tracee can be SIGKILL'ed.  If it
has already passed exit_notify() we can leak a zombie, because a) ptracing
disables the auto-reaping logic, and b) ->real_parent was not notified
about the child's death.

ptrace_detach() should follow the ptrace_exit's logic, change the code
accordingly.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Tested-by: default avatarDenys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b1b4c679

include/linux/ptrace.h

+1 −0
Original line number Diff line number Diff line
@@ -94,6 +94,7 @@ extern void ptrace_notify(int exit_code); 
extern void __ptrace_link(struct task_struct *child,

			  struct task_struct *new_parent);

extern void __ptrace_unlink(struct task_struct *child);

extern int __ptrace_detach(struct task_struct *tracer, struct task_struct *p);

extern void ptrace_fork(struct task_struct *task, unsigned long clone_flags);

#define PTRACE_MODE_READ   1

#define PTRACE_MODE_ATTACH 2

kernel/ptrace.c

+7 −2
Original line number Diff line number Diff line
@@ -237,6 +237,8 @@ out: 


int ptrace_detach(struct task_struct *child, unsigned int data)

{

	int dead = 0;



	if (!valid_signal(data))

		return -EIO;
@@ -244,18 +246,21 @@ int ptrace_detach(struct task_struct *child, unsigned int data) 
	ptrace_disable(child);

	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);



	/* protect against de_thread()->release_task() */

	write_lock_irq(&tasklist_lock);

	/* protect against de_thread()->release_task() */

	if (child->ptrace) {

		child->exit_code = data;



		__ptrace_unlink(child);

		dead = __ptrace_detach(current, child);



		if (!child->exit_state)

			wake_up_process(child);

	}

	write_unlock_irq(&tasklist_lock);



	if (unlikely(dead))

		release_task(child);



	return 0;

}

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