Commit 67850b7b authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'ptrace_stop-cleanup-for-v5.19' of... 

Merge tag 'ptrace_stop-cleanup-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull ptrace_stop cleanups from Eric Biederman:
 "While looking at the ptrace problems with PREEMPT_RT and the problems
  Peter Zijlstra was encountering with ptrace in his freezer rewrite I
  identified some cleanups to ptrace_stop that make sense on their own
  and move make resolving the other problems much simpler.

  The biggest issue is the habit of the ptrace code to change
  task->__state from the tracer to suppress TASK_WAKEKILL from waking up
  the tracee. No other code in the kernel does that and it is straight
  forward to update signal_wake_up and friends to make that unnecessary.

  Peter's task freezer sets frozen tasks to a new state TASK_FROZEN and
  then it stores them by calling "wake_up_state(t, TASK_FROZEN)" relying
  on the fact that all stopped states except the special stop states can
  tolerate spurious wake up and recover their state.

  The state of stopped and traced tasked is changed to be stored in
  task->jobctl as well as in task->__state. This makes it possible for
  the freezer to recover tasks in these special states, as well as
  serving as a general cleanup. With a little more work in that
  direction I believe TASK_STOPPED can learn to tolerate spurious wake
  ups and become an ordinary stop state.

  The TASK_TRACED state has to remain a special state as the registers
  for a process are only reliably available when the process is stopped
  in the scheduler. Fundamentally ptrace needs acess to the saved
  register values of a task.

  There are bunch of semi-random ptrace related cleanups that were found
  while looking at these issues.

  One cleanup that deserves to be called out is from commit 57b6de08
  ("ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs"). This
  makes a change that is technically user space visible, in the handling
  of what happens to a tracee when a tracer dies unexpectedly. According
  to our testing and our understanding of userspace nothing cares that
  spurious SIGTRAPs can be generated in that case"

* tag 'ptrace_stop-cleanup-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  sched,signal,ptrace: Rework TASK_TRACED, TASK_STOPPED state
  ptrace: Always take siglock in ptrace_resume
  ptrace: Don't change __state
  ptrace: Admit ptrace_stop can generate spuriuos SIGTRAPs
  ptrace: Document that wait_task_inactive can't fail
  ptrace: Reimplement PTRACE_KILL by always sending SIGKILL
  signal: Use lockdep_assert_held instead of assert_spin_locked
  ptrace: Remove arch_ptrace_attach
  ptrace/xtensa: Replace PT_SINGLESTEP with TIF_SINGLESTEP
  ptrace/um: Replace PT_DTRACE with TIF_SINGLESTEP
  signal: Replace __group_send_sig_info with send_signal_locked
  signal: Rename send_signal send_signal_locked
parents 1ec6574a 31cae1ea

arch/ia64/include/asm/ptrace.h

+0 −4
Original line number Diff line number Diff line
@@ -139,10 +139,6 @@ static inline long regs_return_value(struct pt_regs *regs) 
  #define arch_ptrace_stop_needed() \

	(!test_thread_flag(TIF_RESTORE_RSE))



  extern void ptrace_attach_sync_user_rbs (struct task_struct *);

  #define arch_ptrace_attach(child) \

	ptrace_attach_sync_user_rbs(child)



  #define arch_has_single_step()  (1)

  #define arch_has_block_step()   (1)

arch/ia64/kernel/ptrace.c

+0 −57
Original line number Diff line number Diff line
@@ -617,63 +617,6 @@ void ia64_sync_krbs(void) 
	unw_init_running(do_sync_rbs, ia64_sync_kernel_rbs);

}



/*

 * After PTRACE_ATTACH, a thread's register backing store area in user

 * space is assumed to contain correct data whenever the thread is

 * stopped.  arch_ptrace_stop takes care of this on tracing stops.

 * But if the child was already stopped for job control when we attach

 * to it, then it might not ever get into ptrace_stop by the time we

 * want to examine the user memory containing the RBS.

 */

void

ptrace_attach_sync_user_rbs (struct task_struct *child)

{

	int stopped = 0;

	struct unw_frame_info info;



	/*

	 * If the child is in TASK_STOPPED, we need to change that to

	 * TASK_TRACED momentarily while we operate on it.  This ensures

	 * that the child won't be woken up and return to user mode while

	 * we are doing the sync.  (It can only be woken up for SIGKILL.)

	 */



	read_lock(&tasklist_lock);

	if (child->sighand) {

		spin_lock_irq(&child->sighand->siglock);

		if (READ_ONCE(child->__state) == TASK_STOPPED &&

		    !test_and_set_tsk_thread_flag(child, TIF_RESTORE_RSE)) {

			set_notify_resume(child);



			WRITE_ONCE(child->__state, TASK_TRACED);

			stopped = 1;

		}

		spin_unlock_irq(&child->sighand->siglock);

	}

	read_unlock(&tasklist_lock);



	if (!stopped)

		return;



	unw_init_from_blocked_task(&info, child);

	do_sync_rbs(&info, ia64_sync_user_rbs);



	/*

	 * Now move the child back into TASK_STOPPED if it should be in a

	 * job control stop, so that SIGCONT can be used to wake it up.

	 */

	read_lock(&tasklist_lock);

	if (child->sighand) {

		spin_lock_irq(&child->sighand->siglock);

		if (READ_ONCE(child->__state) == TASK_TRACED &&

		    (child->signal->flags & SIGNAL_STOP_STOPPED)) {

			WRITE_ONCE(child->__state, TASK_STOPPED);

		}

		spin_unlock_irq(&child->sighand->siglock);

	}

	read_unlock(&tasklist_lock);

}



/*

 * Write f32-f127 back to task->thread.fph if it has been modified.

 */

arch/um/include/asm/thread_info.h

+2 −0
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ static inline struct thread_info *current_thread_info(void) 
#define TIF_RESTORE_SIGMASK	7

#define TIF_NOTIFY_RESUME	8

#define TIF_SECCOMP		9	/* secure computing */

#define TIF_SINGLESTEP		10	/* single stepping userspace */



#define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)

#define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
@@ -68,5 +69,6 @@ static inline struct thread_info *current_thread_info(void) 
#define _TIF_MEMDIE		(1 << TIF_MEMDIE)

#define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)

#define _TIF_SECCOMP		(1 << TIF_SECCOMP)

#define _TIF_SINGLESTEP		(1 << TIF_SINGLESTEP)



#endif

arch/um/kernel/exec.c

+1 −1
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ void start_thread(struct pt_regs *regs, unsigned long eip, unsigned long esp) 
{

	PT_REGS_IP(regs) = eip;

	PT_REGS_SP(regs) = esp;

	current->ptrace &= ~PT_DTRACE;

	clear_thread_flag(TIF_SINGLESTEP);

#ifdef SUBARCH_EXECVE1

	SUBARCH_EXECVE1(regs->regs);

#endif

arch/um/kernel/process.c

+1 −1
Original line number Diff line number Diff line
@@ -336,7 +336,7 @@ int singlestepping(void * t) 
{

	struct task_struct *task = t ? t : current;



	if (!(task->ptrace & PT_DTRACE))

	if (!test_thread_flag(TIF_SINGLESTEP))

		return 0;



	if (task->thread.singlestep_syscall)