Commit f37650f1 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Jan Kara
Browse files

fanotify: fix fsnotify_prepare_user_wait() failure 



If fsnotify_prepare_user_wait() fails, we leave the event on the
notification list.  Which will result in a warning in
fsnotify_destroy_event() and later use-after-free.

Instead of adding a new helper to remove the event from the list in this
case, I opted to move the prepare/finish up into fanotify_handle_event().

This will allow these to be moved further out into the generic code later,
and perhaps let us move to non-sleeping RCU.

Reviewed-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Fixes: 05f0e387 ("fanotify: Release SRCU lock when waiting for userspace response")
Cc: <stable@vger.kernel.org> # v4.12
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent 9a31d7ad

fs/notify/fanotify/fanotify.c

+20 −13
Original line number Diff line number Diff line
@@ -64,19 +64,8 @@ static int fanotify_get_response(struct fsnotify_group *group, 


	pr_debug("%s: group=%p event=%p\n", __func__, group, event);



	/*

	 * fsnotify_prepare_user_wait() fails if we race with mark deletion.

	 * Just let the operation pass in that case.

	 */

	if (!fsnotify_prepare_user_wait(iter_info)) {

		event->response = FAN_ALLOW;

		goto out;

	}



	wait_event(group->fanotify_data.access_waitq, event->response);



	fsnotify_finish_user_wait(iter_info);

out:

	/* userspace responded, convert to something usable */

	switch (event->response) {

	case FAN_ALLOW:
@@ -211,9 +200,21 @@ static int fanotify_handle_event(struct fsnotify_group *group, 
	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,

		 mask);



#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS

	if (mask & FAN_ALL_PERM_EVENTS) {

		/*

		 * fsnotify_prepare_user_wait() fails if we race with mark

		 * deletion.  Just let the operation pass in that case.

		 */

		if (!fsnotify_prepare_user_wait(iter_info))

			return 0;

	}

#endif



	event = fanotify_alloc_event(inode, mask, data);

	ret = -ENOMEM;

	if (unlikely(!event))

		return -ENOMEM;

		goto finish;



	fsn_event = &event->fse;

	ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
@@ -223,7 +224,8 @@ static int fanotify_handle_event(struct fsnotify_group *group, 
		/* Our event wasn't used in the end. Free it. */

		fsnotify_destroy_event(group, fsn_event);



		return 0;

		ret = 0;

		goto finish;

	}



#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
@@ -232,6 +234,11 @@ static int fanotify_handle_event(struct fsnotify_group *group, 
					    iter_info);

		fsnotify_destroy_event(group, fsn_event);

	}

finish:

	if (mask & FAN_ALL_PERM_EVENTS)

		fsnotify_finish_user_wait(iter_info);

#else

finish:

#endif

	return ret;

}

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