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KEYS: reject NULL restriction string when type is specified

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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: 97d3aa0f31 ("KEYS: Add a lookup_restriction function for the asymmetric key type")
Cc: <stable@vger.kernel.org> # v4.12+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
Eric Biggers 2017-12-08 15:13:29 +00:00 committed by David Howells
parent 3d1f025542
commit 18026d8668
1 changed files with 10 additions and 14 deletions
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24
security/keys/keyctl.c
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@ -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_t id, const char __user *_type,
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_t id, const char __user *_type,
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;
}