autofs: sanity check status reported with AUTOFS_DEV_IOCTL_FAIL
If a positive status is passed with the AUTOFS_DEV_IOCTL_FAIL ioctl,
autofs4_d_automount() will return
ERR_PTR(status)
with that status to follow_automount(), which will then dereference an
invalid pointer.
So treat a positive status the same as zero, and map to ENOENT.
See comment in systemd src/core/automount.c::automount_send_ready().
Link: http://lkml.kernel.org/r/871sqwczx5.fsf@notabene.neil.brown.name
Signed-off-by: NeilBrown <neilb at suse.com>
Cc: Ian Kent <raven at themaw.net>
Cc: <stable at vger.kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
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