[PATCH review 03/16] userns: Allow chown and setgid preservation

Eric W. Biederman
2012-11-19T15:13:06Z

- 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.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
fs/attr.c | 11 +++++++----
1 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/attr.c b/fs/attr.c
index cce7df5..1449adb 100644
--- 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;
}
--
1.7.5.4