This is a note to let you know that I've just added the patch titled fanotify: don't expose EOPENSTALE to userspace to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: fanotify-don-t-expose-eopenstale-to-userspace.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 4ff33aafd32e084f5ee7faa54ba06e95f8b1b8af Mon Sep 17 00:00:00 2001 From: Amir Goldstein <amir73il@xxxxxxxxx> Date: Tue, 25 Apr 2017 14:29:35 +0300 Subject: fanotify: don't expose EOPENSTALE to userspace From: Amir Goldstein <amir73il@xxxxxxxxx> commit 4ff33aafd32e084f5ee7faa54ba06e95f8b1b8af upstream. When delivering an event to userspace for a file on an NFS share, if the file is deleted on server side before user reads the event, user will not get the event. If the event queue contained several events, the stale event is quietly dropped and read() returns to user with events read so far in the buffer. If the event queue contains a single stale event or if the stale event is a permission event, read() returns to user with the kernel internal error code 518 (EOPENSTALE), which is not a POSIX error code. Check the internal return value -EOPENSTALE in fanotify_read(), just the same as it is checked in path_openat() and drop the event in the cases that it is not already dropped. This is a reproducer from Marko Rauhamaa: Just take the example program listed under "man fanotify" ("fantest") and follow these steps: ============================================================== NFS Server NFS Client(1) NFS Client(2) ============================================================== # echo foo >/nfsshare/bar.txt # cat /nfsshare/bar.txt foo # ./fantest /nfsshare Press enter key to terminate. Listening for events. # rm -f /nfsshare/bar.txt # cat /nfsshare/bar.txt read: Unknown error 518 cat: /nfsshare/bar.txt: Operation not permitted ============================================================== where NFS Client (1) and (2) are two terminal sessions on a single NFS Client machine. Reported-by: Marko Rauhamaa <marko.rauhamaa@xxxxxxxxxxxx> Tested-by: Marko Rauhamaa <marko.rauhamaa@xxxxxxxxxxxx> Cc: <linux-api@xxxxxxxxxxxxxxx> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/notify/fanotify/fanotify_user.c | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-) --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -294,27 +294,37 @@ static ssize_t fanotify_read(struct file } ret = copy_event_to_user(group, kevent, buf); + if (unlikely(ret == -EOPENSTALE)) { + /* + * We cannot report events with stale fd so drop it. + * Setting ret to 0 will continue the event loop and + * do the right thing if there are no more events to + * read (i.e. return bytes read, -EAGAIN or wait). + */ + ret = 0; + } + /* * Permission events get queued to wait for response. Other * events can be destroyed now. */ if (!(kevent->mask & FAN_ALL_PERM_EVENTS)) { fsnotify_destroy_event(group, kevent); - if (ret < 0) - break; } else { #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS - if (ret < 0) { + if (ret <= 0) { FANOTIFY_PE(kevent)->response = FAN_DENY; wake_up(&group->fanotify_data.access_waitq); - break; + } else { + spin_lock(&group->notification_lock); + list_add_tail(&kevent->list, + &group->fanotify_data.access_list); + spin_unlock(&group->notification_lock); } - spin_lock(&group->notification_lock); - list_add_tail(&kevent->list, - &group->fanotify_data.access_list); - spin_unlock(&group->notification_lock); #endif } + if (ret < 0) + break; buf += ret; count -= ret; } Patches currently in stable-queue which might be from amir73il@xxxxxxxxx are queue-4.9/fanotify-don-t-expose-eopenstale-to-userspace.patch