Commit 5649645d authored Jun 08, 2017 by Eric Biggers Committed by James Morris Jun 09, 2017

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>

parent 0f534e4a

security/keys/keyctl.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -99,7 +99,7 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type,
	/* pull the payload in if one was supplied */		/* pull the payload in if one was supplied */
	payload = NULL;		payload = NULL;

	if (_payload) {		if (plen) {
	ret = -ENOMEM;		ret = -ENOMEM;
	payload = kvmalloc(plen, GFP_KERNEL);		payload = kvmalloc(plen, GFP_KERNEL);
	if (!payload)		if (!payload)
	@@ -324,7 +324,7 @@ long keyctl_update_key(key_serial_t id,

	/* pull the payload in if one was supplied */		/* pull the payload in if one was supplied */
	payload = NULL;		payload = NULL;
	if (_payload) {		if (plen) {
	ret = -ENOMEM;		ret = -ENOMEM;
	payload = kmalloc(plen, GFP_KERNEL);		payload = kmalloc(plen, GFP_KERNEL);
	if (!payload)		if (!payload)