userns: Allow chown and setgid preservation

- Allow chown if CAP_CHOWN is present in the current user namespace
  and the uid of the inode maps into the current user namespace, and
  the destination uid or gid maps into the current user namespace.

- Allow perserving setgid when changing an inode if CAP_FSETID is
  present in the current user namespace and the owner of the file has
  a mapping into the current user namespace.

Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

diff --git a/fs/attr.c b/fs/attr.c
index cce7df53b694373b6288795f14b07eb91c0894fc..1449adb14ef6a468b3d97865499df941a2c28312 100644 (file)
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -49,14 +49,15 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr)
        /* Make sure a caller can chown. */
        if ((ia_valid & ATTR_UID) &&
            (!uid_eq(current_fsuid(), inode->i_uid) ||
-            !uid_eq(attr->ia_uid, inode->i_uid)) && !capable(CAP_CHOWN))
+            !uid_eq(attr->ia_uid, inode->i_uid)) &&
+           !inode_capable(inode, CAP_CHOWN))
                return -EPERM;
 
        /* Make sure caller can chgrp. */
        if ((ia_valid & ATTR_GID) &&
            (!uid_eq(current_fsuid(), inode->i_uid) ||
            (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
-           !capable(CAP_CHOWN))
+           !inode_capable(inode, CAP_CHOWN))
                return -EPERM;
 
        /* Make sure a caller can chmod. */
@@ -65,7 +66,8 @@ int inode_change_ok(const struct inode *inode, struct iattr *attr)
                        return -EPERM;
                /* Also check the setgid bit! */
                if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
-                               inode->i_gid) && !capable(CAP_FSETID))
+                               inode->i_gid) &&
+                   !inode_capable(inode, CAP_FSETID))
                        attr->ia_mode &= ~S_ISGID;
        }
 
@@ -157,7 +159,8 @@ void setattr_copy(struct inode *inode, const struct iattr *attr)
        if (ia_valid & ATTR_MODE) {
                umode_t mode = attr->ia_mode;
 
-               if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
+               if (!in_group_p(inode->i_gid) &&
+                   !inode_capable(inode, CAP_FSETID))
                        mode &= ~S_ISGID;
                inode->i_mode = mode;
        }