KEYS: Change the name of the dead type to ".dead" to prevent user access
authorDavid Howells <dhowells@redhat.com>
Tue, 18 Apr 2017 14:31:08 +0000 (15:31 +0100)
committerDavid Howells <dhowells@redhat.com>
Tue, 18 Apr 2017 14:31:39 +0000 (15:31 +0100)
commitc1644fe041ebaf6519f6809146a77c3ead9193af
tree31ff05d7310b95fbf992b0c3cf328a5e6b0eba83
parentee8f844e3c5a73b999edf733df1c529d6503ec2f
KEYS: Change the name of the dead type to ".dead" to prevent user access

This fixes CVE-2017-6951.

Userspace should not be able to do things with the "dead" key type as it
doesn't have some of the helper functions set upon it that the kernel
needs.  Attempting to use it may cause the kernel to crash.

Fix this by changing the name of the type to ".dead" so that it's rejected
up front on userspace syscalls by key_get_type_from_user().

Though this doesn't seem to affect recent kernels, it does affect older
ones, certainly those prior to:

commit c06cfb08b88dfbe13be44a69ae2fdc3a7c902d81
Author: David Howells <dhowells@redhat.com>
Date:   Tue Sep 16 17:36:06 2014 +0100
KEYS: Remove key_type::match in favour of overriding default by match_preparse

which went in before 3.18-rc1.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: stable@vger.kernel.org
security/keys/gc.c