[PATCH] keys: let keyctl_chown() change a key's owner

Let keyctl_chown() change a key's owner, including attempting to transfer the
quota burden to the new user.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 48 insertions, 8 deletions

diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index d74458522e98..329411cf8768 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -673,6 +673,7 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
  */
 long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
 {
+        struct key_user *newowner, *zapowner = NULL;
         struct key *key;
         key_ref_t key_ref;
         long ret;
@@ -696,19 +697,50 @@ long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
         if (!capable(CAP_SYS_ADMIN)) {
                 /* only the sysadmin can chown a key to some other UID */
                 if (uid != (uid_t) -1 && key->uid != uid)
-                        goto no_access;
+                        goto error_put;
 
                 /* only the sysadmin can set the key's GID to a group other
                  * than one of those that the current process subscribes to */
                 if (gid != (gid_t) -1 && gid != key->gid && !in_group_p(gid))
-                        goto no_access;
+                        goto error_put;
         }
 
-        /* change the UID (have to update the quotas) */
+        /* change the UID */
         if (uid != (uid_t) -1 && uid != key->uid) {
-                /* don't support UID changing yet */
-                ret = -EOPNOTSUPP;
-                goto no_access;
+                ret = -ENOMEM;
+                newowner = key_user_lookup(uid);
+                if (!newowner)
+                        goto error_put;
+
+                /* transfer the quota burden to the new user */
+                if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
+                        spin_lock(&newowner->lock);
+                        if (newowner->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
+                            newowner->qnbytes + key->quotalen >=
+                            KEYQUOTA_MAX_BYTES)
+                                goto quota_overrun;
+
+                        newowner->qnkeys++;
+                        newowner->qnbytes += key->quotalen;
+                        spin_unlock(&newowner->lock);
+
+                        spin_lock(&key->user->lock);
+                        key->user->qnkeys--;
+                        key->user->qnbytes -= key->quotalen;
+                        spin_unlock(&key->user->lock);
+                }
+
+                atomic_dec(&key->user->nkeys);
+                atomic_inc(&newowner->nkeys);
+
+                if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
+                        atomic_dec(&key->user->nikeys);
+                        atomic_inc(&newowner->nikeys);
+                }
+
+                zapowner = key->user;
+                key->user = newowner;
+                key->uid = uid;
         }
 
         /* change the GID */
@@ -717,12 +749,20 @@ long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
 
         ret = 0;
 
- no_access:
+error_put:
         up_write(&key->sem);
         key_put(key);
- error:
+        if (zapowner)
+                key_user_put(zapowner);
+error:
         return ret;
 
+quota_overrun:
+        spin_unlock(&newowner->lock);
+        zapowner = newowner;
+        ret = -EDQUOT;
+        goto error_put;
+
 } /* end keyctl_chown_key() */
 
 /*****************************************************************************/