Return-Path: Received: from fieldses.org ([174.143.236.118]:43908 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756856Ab1IGUzL (ORCPT ); Wed, 7 Sep 2011 16:55:11 -0400 Date: Wed, 7 Sep 2011 16:55:03 -0400 From: "J. Bruce Fields" To: "Aneesh Kumar K.V" Cc: agruen@kernel.org, akpm@linux-foundation.org, dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -V6 11/26] vfs: Add permission flags for setting file attributes Message-ID: <20110907205503.GG8074@fieldses.org> References: <1315243548-18664-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1315243548-18664-12-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Content-Type: text/plain; charset=us-ascii In-Reply-To: <1315243548-18664-12-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Mon, Sep 05, 2011 at 10:55:33PM +0530, Aneesh Kumar K.V wrote: > From: Andreas Gruenbacher > > Some permission models can allow processes to take ownership of a file, > change the file permissions, and set the file timestamps. Introduce new > permission mask flags and check for those permissions in > inode_change_ok(). These little helper functions seem like they might be reasonable cleanup even without the richacl_change_ok() piece; wonder if it'd be worth splitting out the cleanup and applying it now? Not that it's necessary--seems like a straightforward enough patch as is. --b. > > Signed-off-by: Andreas Gruenbacher > Signed-off-by: Aneesh Kumar K.V > --- > fs/attr.c | 70 +++++++++++++++++++++++++++++++++++++++++++-------- > fs/namei.c | 2 +- > include/linux/fs.h | 4 +++ > 3 files changed, 64 insertions(+), 12 deletions(-) > > diff --git a/fs/attr.c b/fs/attr.c > index f15e9e3..00578b9 100644 > --- a/fs/attr.c > +++ b/fs/attr.c > @@ -14,6 +14,55 @@ > #include > #include > > +static int richacl_change_ok(struct inode *inode, int mask) > +{ > + if (!IS_RICHACL(inode)) > + return -EPERM; > + > + if (inode->i_op->permission) > + return inode->i_op->permission(inode, mask); > + > + return check_acl(inode, mask); > +} > + > +static bool inode_uid_change_ok(struct inode *inode, uid_t ia_uid) > +{ > + if (current_fsuid() == inode->i_uid && ia_uid == inode->i_uid) > + return true; > + if (current_fsuid() == ia_uid && > + richacl_change_ok(inode, MAY_TAKE_OWNERSHIP) == 0) > + return true; > + if (capable(CAP_CHOWN)) > + return true; > + return false; > +} > + > +static bool inode_gid_change_ok(struct inode *inode, gid_t ia_gid) > +{ > + int in_group = in_group_p(ia_gid); > + if (current_fsuid() == inode->i_uid && > + (in_group || ia_gid == inode->i_gid)) > + return true; > + if (in_group && richacl_change_ok(inode, MAY_TAKE_OWNERSHIP) == 0) > + return true; > + if (capable(CAP_CHOWN)) > + return true; > + return false; > +} > + > +static bool inode_owner_permitted_or_capable(struct inode *inode, int mask) > +{ > + struct user_namespace *ns = inode_userns(inode); > + > + if (current_user_ns() == ns && current_fsuid() == inode->i_uid) > + return true; > + if (richacl_change_ok(inode, mask) == 0) > + return true; > + if (ns_capable(ns, CAP_FOWNER)) > + return true; > + return false; > +} > + > /** > * inode_change_ok - check if attribute changes to an inode are allowed > * @inode: inode to check > @@ -45,21 +94,20 @@ int inode_change_ok(struct inode *inode, struct iattr *attr) > return 0; > > /* Make sure a caller can chown. */ > - if ((ia_valid & ATTR_UID) && > - (current_fsuid() != inode->i_uid || > - attr->ia_uid != inode->i_uid) && !capable(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) && > - (current_fsuid() != inode->i_uid || > - (!in_group_p(attr->ia_gid) && attr->ia_gid != inode->i_gid)) && > - !capable(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 : > @@ -69,7 +117,7 @@ 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/fs/namei.c b/fs/namei.c > index eacb530..a4d61d1 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -174,7 +174,7 @@ void putname(const char *name) > EXPORT_SYMBOL(putname); > #endif > > -static int check_acl(struct inode *inode, int mask) > +int check_acl(struct inode *inode, int mask) > { > #ifdef CONFIG_FS_POSIX_ACL > struct posix_acl *acl; > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 8afb054..8d5d6e4 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -71,6 +71,9 @@ struct inodes_stat_t { > #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 > @@ -2234,6 +2237,7 @@ extern sector_t bmap(struct inode *, sector_t); > extern int notify_change(struct dentry *, struct iattr *); > extern int inode_permission(struct inode *, int); > extern int generic_permission(struct inode *, int); > +extern int check_acl(struct inode *, int); > > static inline bool execute_ok(struct inode *inode) > { > -- > 1.7.4.1 >