Commit 17b439db authored by Beau Belgrave's avatar Beau Belgrave Committed by Steven Rostedt (Google)
Browse files

tracing/user_events: Ensure bit is cleared on unregister 

If an event is enabled and a user process unregisters user_events, the
bit is left set. Fix this by always clearing the bit in the user process
if unregister is successful.

Update abi self-test to ensure this occurs properly.

Link: https://lkml.kernel.org/r/20230425225107.8525-3-beaub@linux.microsoft.com



Suggested-by: default avatarDoug Cook <dcook@linux.microsoft.com>
Signed-off-by: default avatarBeau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent cd98c932

kernel/trace/trace_events_user.c

+34 −0
Original line number Diff line number Diff line
@@ -2149,6 +2149,35 @@ static long user_unreg_get(struct user_unreg __user *ureg, 
	return ret;

}



static int user_event_mm_clear_bit(struct user_event_mm *user_mm,

				   unsigned long uaddr, unsigned char bit)

{

	struct user_event_enabler enabler;

	int result;



	memset(&enabler, 0, sizeof(enabler));

	enabler.addr = uaddr;

	enabler.values = bit;

retry:

	/* Prevents state changes from racing with new enablers */

	mutex_lock(&event_mutex);



	/* Force the bit to be cleared, since no event is attached */

	mmap_read_lock(user_mm->mm);

	result = user_event_enabler_write(user_mm, &enabler, false);

	mmap_read_unlock(user_mm->mm);



	mutex_unlock(&event_mutex);



	if (result) {

		/* Attempt to fault-in and retry if it worked */

		if (!user_event_mm_fault_in(user_mm, uaddr))

			goto retry;

	}



	return result;

}



/*

 * Unregisters an enablement address/bit within a task/user mm.

 */
@@ -2193,6 +2222,11 @@ static long user_events_ioctl_unreg(unsigned long uarg) 


	mutex_unlock(&event_mutex);



	/* Ensure bit is now cleared for user, regardless of event status */

	if (!ret)

		ret = user_event_mm_clear_bit(mm, reg.disable_addr,

					      reg.disable_bit);



	return ret;

}

tools/testing/selftests/user_events/abi_test.c

+6 −3
Original line number Diff line number Diff line
@@ -109,13 +109,16 @@ TEST_F(user, enablement) { 
	ASSERT_EQ(0, change_event(false));

	ASSERT_EQ(0, self->check);



	/* Should not change after disable */

	/* Ensure kernel clears bit after disable */

	ASSERT_EQ(0, change_event(true));

	ASSERT_EQ(1, self->check);

	ASSERT_EQ(0, reg_disable(&self->check, 0));

	ASSERT_EQ(0, self->check);



	/* Ensure doesn't change after unreg */

	ASSERT_EQ(0, change_event(true));

	ASSERT_EQ(0, self->check);

	ASSERT_EQ(0, change_event(false));

	ASSERT_EQ(1, self->check);

	self->check = 0;

}



TEST_F(user, bit_sizes) {