From: Andreas Gruenbacher Subject: [PATCH v18 05/22] vfs: Add permission flags for setting file attributes Date: Mon, 29 Feb 2016 09:17:10 +0100 Message-ID: <1456733847-17982-6-git-send-email-agruenba@redhat.com> References: <1456733847-17982-1-git-send-email-agruenba@redhat.com> Cc: "J. Bruce Fields" , linux-nfs@vger.kernel.org, "Theodore Ts'o" , linux-cifs@vger.kernel.org, linux-api@vger.kernel.org, Trond Myklebust , linux-kernel@vger.kernel.org, xfs@oss.sgi.com, Christoph Hellwig , Andreas Dilger , linux-fsdevel@vger.kernel.org, Jeff Layton , linux-ext4@vger.kernel.org, Anna Schumaker To: Alexander Viro Return-path: In-Reply-To: <1456733847-17982-1-git-send-email-agruenba@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Richacls support permissions that allow to take ownership of a file, change the file permissions, and set the file timestamps. Support that by introducing new permission mask flags and by checking for those mask flags in inode_change_ok(). Signed-off-by: Andreas Gruenbacher Reviewed-by: J. Bruce Fields --- fs/attr.c | 79 +++++++++++++++++++++++++++++++++++++++++++++--------- include/linux/fs.h | 3 +++ 2 files changed, 70 insertions(+), 12 deletions(-) diff --git a/fs/attr.c b/fs/attr.c index 7ca7fa0..2a8c49c 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -17,6 +17,65 @@ #include /** + * inode_extended_permission - permissions beyond read/write/execute + * + * Check for permissions that only richacls can currently grant. + */ +static int inode_extended_permission(struct inode *inode, int mask) +{ + if (!IS_RICHACL(inode)) + return -EPERM; + return inode_permission(inode, mask); +} + +static bool inode_uid_change_ok(struct inode *inode, kuid_t ia_uid) +{ + if (uid_eq(current_fsuid(), inode->i_uid) && + uid_eq(ia_uid, inode->i_uid)) + return true; + if (uid_eq(current_fsuid(), ia_uid) && + inode_extended_permission(inode, MAY_TAKE_OWNERSHIP) == 0) + return true; + if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) + return true; + return false; +} + +static bool inode_gid_change_ok(struct inode *inode, kgid_t ia_gid) +{ + int in_group = in_group_p(ia_gid); + if (uid_eq(current_fsuid(), inode->i_uid) && + (in_group || gid_eq(ia_gid, inode->i_gid))) + return true; + if (in_group && inode_extended_permission(inode, MAY_TAKE_OWNERSHIP) == 0) + return true; + if (capable_wrt_inode_uidgid(inode, CAP_CHOWN)) + return true; + return false; +} + +/** + * inode_owner_permitted_or_capable + * + * Check for permissions implicitly granted to the owner, like MAY_CHMOD or + * MAY_SET_TIMES. Equivalent to inode_owner_or_capable for file systems + * without support for those permissions. + */ +static bool inode_owner_permitted_or_capable(struct inode *inode, int mask) +{ + struct user_namespace *ns; + + if (uid_eq(current_fsuid(), inode->i_uid)) + return true; + if (inode_extended_permission(inode, mask) == 0) + return true; + ns = current_user_ns(); + if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid)) + return true; + return false; +} + +/** * inode_change_ok - check if attribute changes to an inode are allowed * @inode: inode to check * @attr: attributes to change @@ -47,22 +106,18 @@ int inode_change_ok(struct inode *inode, struct iattr *attr) return 0; /* 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_wrt_inode_uidgid(inode, CAP_CHOWN)) - return -EPERM; + if (ia_valid & ATTR_UID) + if (!inode_uid_change_ok(inode, attr->ia_uid)) + 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_wrt_inode_uidgid(inode, CAP_CHOWN)) - return -EPERM; + if (ia_valid & ATTR_GID) + if (!inode_gid_change_ok(inode, attr->ia_gid)) + return -EPERM; /* Make sure a caller can chmod. */ if (ia_valid & ATTR_MODE) { - if (!inode_owner_or_capable(inode)) + if (!inode_owner_permitted_or_capable(inode, MAY_CHMOD)) return -EPERM; /* Also check the setgid bit! */ if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid : @@ -73,7 +128,7 @@ int inode_change_ok(struct inode *inode, struct iattr *attr) /* Check for setting the inode time. */ if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) { - if (!inode_owner_or_capable(inode)) + if (!inode_owner_permitted_or_capable(inode, MAY_SET_TIMES)) return -EPERM; } diff --git a/include/linux/fs.h b/include/linux/fs.h index efff04f..0f560b7 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -87,6 +87,9 @@ typedef void (dax_iodone_t)(struct buffer_head *bh_map, int uptodate); #define MAY_CREATE_DIR 0x00000200 #define MAY_DELETE_CHILD 0x00000400 #define MAY_DELETE_SELF 0x00000800 +#define MAY_TAKE_OWNERSHIP 0x00001000 +#define MAY_CHMOD 0x00002000 +#define MAY_SET_TIMES 0x00004000 /* * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond -- 2.4.3