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Subject[PATCH 4.14 043/164] KEYS: reject NULL restriction string when type is specified
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@google.com>

commit 18026d866801d0c52e5550210563222bd6c7191d upstream.

keyctl_restrict_keyring() allows through a NULL restriction when the
"type" is non-NULL, which causes a NULL pointer dereference in
asymmetric_lookup_restriction() when it calls strcmp() on the
restriction string.

But no key types actually use a "NULL restriction" to mean anything, so
update keyctl_restrict_keyring() to reject it with EINVAL.

Reported-by: syzbot <syzkaller@googlegroups.com>
Fixes: 97d3aa0f3134 ("KEYS: Add a lookup_restriction function for the asymmetric key type")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
security/keys/keyctl.c | 24 ++++++++++--------------
1 file changed, 10 insertions(+), 14 deletions(-)

--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1588,9 +1588,8 @@ error_keyring:
* The caller must have Setattr permission to change keyring restrictions.
*
* The requested type name may be a NULL pointer to reject all attempts
- * to link to the keyring. If _type is non-NULL, _restriction can be
- * NULL or a pointer to a string describing the restriction. If _type is
- * NULL, _restriction must also be NULL.
+ * to link to the keyring. In this case, _restriction must also be NULL.
+ * Otherwise, both _type and _restriction must be non-NULL.
*
* Returns 0 if successful.
*/
@@ -1598,7 +1597,6 @@ long keyctl_restrict_keyring(key_serial_
const char __user *_restriction)
{
key_ref_t key_ref;
- bool link_reject = !_type;
char type[32];
char *restriction = NULL;
long ret;
@@ -1607,31 +1605,29 @@ long keyctl_restrict_keyring(key_serial_
if (IS_ERR(key_ref))
return PTR_ERR(key_ref);

+ ret = -EINVAL;
if (_type) {
+ if (!_restriction)
+ goto error;
+
ret = key_get_type_from_user(type, _type, sizeof(type));
if (ret < 0)
goto error;
- }
-
- if (_restriction) {
- if (!_type) {
- ret = -EINVAL;
- goto error;
- }

restriction = strndup_user(_restriction, PAGE_SIZE);
if (IS_ERR(restriction)) {
ret = PTR_ERR(restriction);
goto error;
}
+ } else {
+ if (_restriction)
+ goto error;
}

- ret = keyring_restrict(key_ref, link_reject ? NULL : type, restriction);
+ ret = keyring_restrict(key_ref, _type ? type : NULL, restriction);
kfree(restriction);
-
error:
key_ref_put(key_ref);
-
return ret;
}


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