KEYS: special dot prefixed keyring name bug fix

Dot prefixed keyring names are supposed to be reserved for the
kernel, but add_key() calls key_get_type_from_user(), which
incorrectly verifies the 'type' field, not the 'description' field.
This patch verifies the 'description' field isn't dot prefixed,
when creating a new keyring, and removes the dot prefix test in
key_get_type_from_user().

Changelog v6:
- whitespace and other cleanup

Changelog v5:
- Only prevent userspace from creating a dot prefixed keyring, not
  regular keys  - Dmitry

Reported-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index cd5bd0cef25d..8a8c23357291 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -37,8 +37,6 @@ static int key_get_type_from_user(char *type,
                 return ret;
         if (ret == 0 || ret >= len)
                 return -EINVAL;
-        if (type[0] == '.')
-                return -EPERM;
         type[len - 1] = '\0';
         return 0;
 }
@@ -86,6 +84,10 @@ SYSCALL_DEFINE5(add_key, const char __user *, _type,
                 if (!*description) {
                         kfree(description);
                         description = NULL;
+                } else if ((description[0] == '.') &&
+                           (strncmp(type, "keyring", 7) == 0)) {
+                        ret = -EPERM;
+                        goto error2;
                 }
         }