Return-Path: Received: from fieldses.org ([174.143.236.118]:36299 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756348Ab1IGUkM (ORCPT ); Wed, 7 Sep 2011 16:40:12 -0400 Date: Wed, 7 Sep 2011 16:39:16 -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 09/26] vfs: Add delete child and delete self permission flags Message-ID: <20110907203916.GE8074@fieldses.org> References: <1315243548-18664-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1315243548-18664-10-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Content-Type: text/plain; charset=us-ascii In-Reply-To: <1315243548-18664-10-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 10:55:31PM +0530, Aneesh Kumar K.V wrote: > From: Andreas Gruenbacher > > Normally, deleting a file requires write access to the parent directory. > Some permission models use a different permission on the parent > directory to indicate delete access. In addition, a process can have > per-file delete access even without delete access on the parent > directory. > > Introduce two new inode_permission() mask flags and use them in > may_delete() > > Signed-off-by: Andreas Gruenbacher > Signed-off-by: Aneesh Kumar K.V > --- > fs/namei.c | 41 +++++++++++++++++++++++++++-------------- > include/linux/fs.h | 2 ++ > 2 files changed, 29 insertions(+), 14 deletions(-) > > diff --git a/fs/namei.c b/fs/namei.c > index d52a4cd..eacb530 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -337,7 +337,7 @@ static inline int do_inode_permission(struct inode *inode, int mask) > * are used for other things. > * > * When checking for MAY_APPEND, MAY_CREATE_FILE, MAY_CREATE_DIR, > - * MAY_WRITE must also be set in @mask. > + * MAY_DELETE_CHILD, MAY_DELETE_SELF, MAY_WRITE must also be set in @mask. > */ > int inode_permission(struct inode *inode, int mask) > { > @@ -1862,7 +1862,7 @@ static inline int check_sticky(struct inode *dir, struct inode *inode) > return 0; > > other_userns: > - return !ns_capable(inode_userns(inode), CAP_FOWNER); > + return 1; > } > > /* > @@ -1884,30 +1884,43 @@ other_userns: > * 10. We don't allow removal of NFS sillyrenamed files; it's handled by > * nfs_async_unlink(). > */ > -static int may_delete(struct inode *dir,struct dentry *victim,int isdir) > +static int may_delete(struct inode *dir, struct dentry *victim, > + int isdir, int replace) > { > - int error; > + int mask, error, is_sticky; > + struct inode *inode = victim->d_inode; > > - if (!victim->d_inode) > + if (!inode) > return -ENOENT; > > BUG_ON(victim->d_parent->d_inode != dir); > audit_inode_child(victim, dir); > > - error = inode_permission(dir, MAY_WRITE | MAY_EXEC); > + mask = MAY_WRITE | MAY_EXEC | MAY_DELETE_CHILD; > + if (replace) > + mask |= S_ISDIR(inode->i_mode) ? > + MAY_CREATE_DIR : MAY_CREATE_FILE; I'm having trouble understanding this next bit: > + is_sticky = check_sticky(dir, inode); > + error = inode_permission(dir, mask); > + if ((error || is_sticky) && IS_RICHACL(inode) && > + !inode_permission(dir, mask & ~(MAY_WRITE | MAY_DELETE_CHILD)) && > + !inode_permission(inode, MAY_DELETE_SELF)) > + error = 0; OK, so we can ignore the lack of write or delete permissions on the parent if we have delete_self permissions on the child. I guess that's right. Why the "|| is_sticky" above? Is there some less complicated why to write this? --b. > + else if (!error && is_sticky && > + !ns_capable(inode_userns(inode), CAP_FOWNER)) > + error = -EPERM; > if (error) > return error; > if (IS_APPEND(dir)) > return -EPERM; > - if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)|| > - IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode)) > + if (IS_APPEND(inode) || IS_IMMUTABLE(inode) || IS_SWAPFILE(inode)) > return -EPERM; > if (isdir) { > - if (!S_ISDIR(victim->d_inode->i_mode)) > + if (!S_ISDIR(inode->i_mode)) > return -ENOTDIR; > if (IS_ROOT(victim)) > return -EBUSY; > - } else if (S_ISDIR(victim->d_inode->i_mode)) > + } else if (S_ISDIR(inode->i_mode)) > return -EISDIR; > if (IS_DEADDIR(dir)) > return -ENOENT; > @@ -2614,7 +2627,7 @@ void dentry_unhash(struct dentry *dentry) > > int vfs_rmdir(struct inode *dir, struct dentry *dentry) > { > - int error = may_delete(dir, dentry, 1); > + int error = may_delete(dir, dentry, 1, 0); > > if (error) > return error; > @@ -2707,7 +2720,7 @@ SYSCALL_DEFINE1(rmdir, const char __user *, pathname) > > int vfs_unlink(struct inode *dir, struct dentry *dentry) > { > - int error = may_delete(dir, dentry, 0); > + int error = may_delete(dir, dentry, 0, 0); > > if (error) > return error; > @@ -3101,14 +3114,14 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, > if (old_dentry->d_inode == new_dentry->d_inode) > return 0; > > - error = may_delete(old_dir, old_dentry, is_dir); > + error = may_delete(old_dir, old_dentry, is_dir, 0); > if (error) > return error; > > if (!new_dentry->d_inode) > error = may_create(new_dir, new_dentry, is_dir); > else > - error = may_delete(new_dir, new_dentry, is_dir); > + error = may_delete(new_dir, new_dentry, is_dir, 1); > if (error) > return error; > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 8707f43..c5c98c5 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -69,6 +69,8 @@ struct inodes_stat_t { > #define MAY_NOT_BLOCK 0x00000080 > #define MAY_CREATE_FILE 0x00000100 > #define MAY_CREATE_DIR 0x00000200 > +#define MAY_DELETE_CHILD 0x00000400 > +#define MAY_DELETE_SELF 0x00000800 > > /* > * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond > -- > 1.7.4.1 >