Eric,
On Thu, 30 Nov 2017, Eric Biggers wrote:
From: Eric Biggers <ebiggers@xxxxxxxxxx>
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.
Since this fixes the bug for the asymmetric key type and ensures that
other key types won't make the same mistake, I agree this is the way to
fix it. I did not find any issues in the patch.
Thanks,
Mat
Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
Fixes: 97d3aa0f3134 ("KEYS: Add a lookup_restriction function for the asymmetric key type")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.12+
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
security/keys/keyctl.c | 24 ++++++++++--------------
1 file changed, 10 insertions(+), 14 deletions(-)
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 76d22f726ae4..1ffe60bb2845 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1588,9 +1588,8 @@ long keyctl_session_to_parent(void)
* 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) {
- ret = key_get_type_from_user(type, _type, sizeof(type));
- if (ret < 0)
+ if (!_restriction)
goto error;
- }
- if (_restriction) {
- if (!_type) {
- ret = -EINVAL;
+ ret = key_get_type_from_user(type, _type, sizeof(type));
+ if (ret < 0)
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;
}
--
2.15.0.531.g2ccb3012c9-goog
--
Mat Martineau
Intel OTC