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Commit fd76b2d5 authored by Andrei Vagin's avatar Andrei Vagin Committed by Greg Kroah-Hartman
Browse files

ptrace: take into account saved_sigmask in PTRACE{GET,SET}SIGMASK 

[ Upstream commit fcfc2aa0185f4a731d05a21e9f359968fdfd02e7 ]

There are a few system calls (pselect, ppoll, etc) which replace a task
sigmask while they are running in a kernel-space

When a task calls one of these syscalls, the kernel saves a current
sigmask in task->saved_sigmask and sets a syscall sigmask.

On syscall-exit-stop, ptrace traps a task before restoring the
saved_sigmask, so PTRACE_GETSIGMASK returns the syscall sigmask and
PTRACE_SETSIGMASK does nothing, because its sigmask is replaced by
saved_sigmask, when the task returns to user-space.

This patch fixes this problem.  PTRACE_GETSIGMASK returns saved_sigmask
if it's set.  PTRACE_SETSIGMASK drops the TIF_RESTORE_SIGMASK flag.

Link: http://lkml.kernel.org/r/20181120060616.6043-1-avagin@gmail.com


Fixes: 29000cae ("ptrace: add ability to get/set signal-blocked mask")
Signed-off-by: default avatarAndrei Vagin <avagin@gmail.com>
Acked-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarSasha Levin (Microsoft) <sashal@kernel.org>
parent 0af211ec

include/linux/sched/signal.h

+18 −0
Original line number Diff line number Diff line
@@ -377,10 +377,20 @@ static inline void set_restore_sigmask(void) 
	set_thread_flag(TIF_RESTORE_SIGMASK);

	WARN_ON(!test_thread_flag(TIF_SIGPENDING));

}



static inline void clear_tsk_restore_sigmask(struct task_struct *tsk)

{

	clear_tsk_thread_flag(tsk, TIF_RESTORE_SIGMASK);

}



static inline void clear_restore_sigmask(void)

{

	clear_thread_flag(TIF_RESTORE_SIGMASK);

}

static inline bool test_tsk_restore_sigmask(struct task_struct *tsk)

{

	return test_tsk_thread_flag(tsk, TIF_RESTORE_SIGMASK);

}

static inline bool test_restore_sigmask(void)

{

	return test_thread_flag(TIF_RESTORE_SIGMASK);
@@ -398,6 +408,10 @@ static inline void set_restore_sigmask(void) 
	current->restore_sigmask = true;

	WARN_ON(!test_thread_flag(TIF_SIGPENDING));

}

static inline void clear_tsk_restore_sigmask(struct task_struct *tsk)

{

	tsk->restore_sigmask = false;

}

static inline void clear_restore_sigmask(void)

{

	current->restore_sigmask = false;
@@ -406,6 +420,10 @@ static inline bool test_restore_sigmask(void) 
{

	return current->restore_sigmask;

}

static inline bool test_tsk_restore_sigmask(struct task_struct *tsk)

{

	return tsk->restore_sigmask;

}

static inline bool test_and_clear_restore_sigmask(void)

{

	if (!current->restore_sigmask)

kernel/ptrace.c

+13 −2
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ 
#include <linux/hw_breakpoint.h>

#include <linux/cn_proc.h>

#include <linux/compat.h>

#include <linux/sched/signal.h>



/*

 * Access another process' address space via ptrace.
@@ -925,18 +926,26 @@ int ptrace_request(struct task_struct *child, long request, 
			ret = ptrace_setsiginfo(child, &siginfo);

		break;



	case PTRACE_GETSIGMASK:

	case PTRACE_GETSIGMASK: {

		sigset_t *mask;



		if (addr != sizeof(sigset_t)) {

			ret = -EINVAL;

			break;

		}



		if (copy_to_user(datavp, &child->blocked, sizeof(sigset_t)))

		if (test_tsk_restore_sigmask(child))

			mask = &child->saved_sigmask;

		else

			mask = &child->blocked;



		if (copy_to_user(datavp, mask, sizeof(sigset_t)))

			ret = -EFAULT;

		else

			ret = 0;



		break;

	}



	case PTRACE_SETSIGMASK: {

		sigset_t new_set;
@@ -962,6 +971,8 @@ int ptrace_request(struct task_struct *child, long request, 
		child->blocked = new_set;

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



		clear_tsk_restore_sigmask(child);



		ret = 0;

		break;

	}