This is a note to let you know that I've just added the patch titled

fanotify: fix fsnotify_prepare_user_wait() failure

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: fanotify-fix-fsnotify_prepare_user_wait-failure.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From f37650f1c7c71cf5180b43229d13b421d81e7170 Mon Sep 17 00:00:00 2001

From: Miklos Szeredi mszeredi@redhat.com Date: Mon, 30 Oct 2017 21:14:56 +0100 Subject: fanotify: fix fsnotify_prepare_user_wait() failure

From: Miklos Szeredi mszeredi@redhat.com

commit f37650f1c7c71cf5180b43229d13b421d81e7170 upstream.

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: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Fixes: 05f0e38724e8 ("fanotify: Release SRCU lock when waiting for userspace response") Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- fs/notify/fanotify/fanotify.c | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-)

--- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -65,19 +65,8 @@ static int fanotify_get_response(struct

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: @@ -212,9 +201,21 @@ static int fanotify_handle_event(struct 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); @@ -224,7 +225,8 @@ static int fanotify_handle_event(struct /* 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 @@ -233,6 +235,11 @@ static int fanotify_handle_event(struct 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; }

Patches currently in stable-queue which might be from mszeredi@redhat.com are

queue-4.14/fsnotify-clean-up-fsnotify_prepare-finish_user_wait.patch queue-4.14/fsnotify-fix-pinning-group-in-fsnotify_prepare_user_wait.patch queue-4.14/fanotify-fix-fsnotify_prepare_user_wait-failure.patch queue-4.14/fsnotify-pin-both-inode-and-vfsmount-mark.patch queue-4.14/ovl-put-upperdentry-if-ovl_check_origin-fails.patch