KEYS: fix dereferencing NULL payload with nonzero length
authorEric Biggers <ebiggers@google.com>
Thu, 8 Jun 2017 13:48:40 +0000 (14:48 +0100)
committerJames Morris <james.l.morris@oracle.com>
Fri, 9 Jun 2017 03:29:47 +0000 (13:29 +1000)
commit5649645d725c73df4302428ee4e02c869248b4c5
tree14116cd39ec4d20e8656e22a108d3691a46e37d3
parent0f534e4a13496b02ae284f50fcb0263f6ea37007
KEYS: fix dereferencing NULL payload with nonzero length

sys_add_key() and the KEYCTL_UPDATE operation of sys_keyctl() allowed a
NULL payload with nonzero length to be passed to the key type's
->preparse(), ->instantiate(), and/or ->update() methods.  Various key
types including asymmetric, cifs.idmap, cifs.spnego, and pkcs7_test did
not handle this case, allowing an unprivileged user to trivially cause a
NULL pointer dereference (kernel oops) if one of these key types was
present.  Fix it by doing the copy_from_user() when 'plen' is nonzero
rather than when '_payload' is non-NULL, causing the syscall to fail
with EFAULT as expected when an invalid buffer is specified.

Cc: stable@vger.kernel.org # 2.6.10+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
security/keys/keyctl.c