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

Serge Hallyn
2012-11-19T17:50:03Z

Quoting Eric W. Biederman (ebiederm@xmission.com):
> From: "Eric W. Biederman" <ebiederm@xmission.com>
>
> - 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>

Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.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
>
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