From patchwork Sat Mar 20 21:51:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 12152667 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D3BAC433DB for ; Sat, 20 Mar 2021 21:54:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D6A696191A for ; Sat, 20 Mar 2021 21:54:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229817AbhCTVyW (ORCPT ); Sat, 20 Mar 2021 17:54:22 -0400 Received: from zeniv-ca.linux.org.uk ([142.44.231.140]:35554 "EHLO zeniv-ca.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229460AbhCTVxz (ORCPT ); Sat, 20 Mar 2021 17:53:55 -0400 Received: from viro by zeniv-ca.linux.org.uk with local (Exim 4.94 #2 (Red Hat Linux)) id 1lNjVW-007jXu-Hj; Sat, 20 Mar 2021 21:51:42 +0000 Date: Sat, 20 Mar 2021 21:51:42 +0000 From: Al Viro To: Tyler Hicks Cc: ecryptfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH 2/4] ecryptfs: saner API for lock_parent() Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Sender: Al Viro Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Switch all users of lock_parent() to the approach used by ->unlink() and ->rmdir() - instead of playing with dget_parent() of underlying dentry of child, * start with ecryptfs dentry of child. * find underlying dentries for that dentry and its parent (which is stable, since the parent directory in upper layer is held at least shared). No need to pin them, they are already pinned by ecryptfs dentries. * lock the inode of undelying directory of parent * check if it's the parent of underlying dentry of child. ->d_parent of underlying dentry of child might be unstable. However, result of its comparison with underlying dentry of parent *is* stable now. Turn that into replacement of lock_parent(), convert the existing callers of lock_parent() to that, along with ecryptfs_unlink() and ecryptfs_rmdir(). Callers need only the underlying dentry of child and inode of underlying dentry of parent, so lock_parent() passes those to the caller now. Note that underlying directory is locked in any case, success or failure. That approach does not need a primitive for unlocking - we hadn't grabbed any dentry references, so all we need is to unlock the underlying directory inode. Signed-off-by: Al Viro --- fs/ecryptfs/inode.c | 157 +++++++++++++++++++++++++--------------------------- 1 file changed, 74 insertions(+), 83 deletions(-) diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c index 689aa493e587..861a01713f3f 100644 --- a/fs/ecryptfs/inode.c +++ b/fs/ecryptfs/inode.c @@ -21,19 +21,18 @@ #include #include "ecryptfs_kernel.h" -static struct dentry *lock_parent(struct dentry *dentry) +static int lock_parent(struct dentry *dentry, + struct dentry **lower_dentry, + struct inode **lower_dir) { - struct dentry *dir; + struct dentry *lower_dir_dentry; - dir = dget_parent(dentry); - inode_lock_nested(d_inode(dir), I_MUTEX_PARENT); - return dir; -} + lower_dir_dentry = ecryptfs_dentry_to_lower(dentry->d_parent); + *lower_dir = d_inode(lower_dir_dentry); + *lower_dentry = ecryptfs_dentry_to_lower(dentry); -static void unlock_dir(struct dentry *dir) -{ - inode_unlock(d_inode(dir)); - dput(dir); + inode_lock_nested(*lower_dir, I_MUTEX_PARENT); + return (*lower_dentry)->d_parent == lower_dir_dentry ? 0 : -EINVAL; } static int ecryptfs_inode_test(struct inode *inode, void *lower_inode) @@ -127,32 +126,29 @@ static int ecryptfs_interpose(struct dentry *lower_dentry, static int ecryptfs_do_unlink(struct inode *dir, struct dentry *dentry, struct inode *inode) { - struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry); - struct dentry *lower_dir_dentry; - struct inode *lower_dir_inode; + struct dentry *lower_dentry; + struct inode *lower_dir; int rc; - lower_dir_dentry = ecryptfs_dentry_to_lower(dentry->d_parent); - lower_dir_inode = d_inode(lower_dir_dentry); - inode_lock_nested(lower_dir_inode, I_MUTEX_PARENT); + rc = lock_parent(dentry, &lower_dentry, &lower_dir); dget(lower_dentry); // don't even try to make the lower negative - if (lower_dentry->d_parent != lower_dir_dentry) - rc = -EINVAL; - else if (d_unhashed(lower_dentry)) - rc = -EINVAL; - else - rc = vfs_unlink(&init_user_ns, lower_dir_inode, lower_dentry, - NULL); + if (!rc) { + if (d_unhashed(lower_dentry)) + rc = -EINVAL; + else + rc = vfs_unlink(&init_user_ns, lower_dir, lower_dentry, + NULL); + } if (rc) { printk(KERN_ERR "Error in vfs_unlink; rc = [%d]\n", rc); goto out_unlock; } - fsstack_copy_attr_times(dir, lower_dir_inode); + fsstack_copy_attr_times(dir, lower_dir); set_nlink(inode, ecryptfs_inode_to_lower(inode)->i_nlink); inode->i_ctime = dir->i_ctime; out_unlock: dput(lower_dentry); - inode_unlock(lower_dir_inode); + inode_unlock(lower_dir); if (!rc) d_drop(dentry); return rc; @@ -176,13 +172,13 @@ ecryptfs_do_create(struct inode *directory_inode, { int rc; struct dentry *lower_dentry; - struct dentry *lower_dir_dentry; + struct inode *lower_dir; struct inode *inode; - lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry); - lower_dir_dentry = lock_parent(lower_dentry); - rc = vfs_create(&init_user_ns, d_inode(lower_dir_dentry), lower_dentry, - mode, true); + rc = lock_parent(ecryptfs_dentry, &lower_dentry, &lower_dir); + if (!rc) + rc = vfs_create(&init_user_ns, lower_dir, + lower_dentry, mode, true); if (rc) { printk(KERN_ERR "%s: Failure to create dentry in lower fs; " "rc = [%d]\n", __func__, rc); @@ -192,14 +188,13 @@ ecryptfs_do_create(struct inode *directory_inode, inode = __ecryptfs_get_inode(d_inode(lower_dentry), directory_inode->i_sb); if (IS_ERR(inode)) { - vfs_unlink(&init_user_ns, d_inode(lower_dir_dentry), - lower_dentry, NULL); + vfs_unlink(&init_user_ns, lower_dir, lower_dentry, NULL); goto out_lock; } - fsstack_copy_attr_times(directory_inode, d_inode(lower_dir_dentry)); - fsstack_copy_inode_size(directory_inode, d_inode(lower_dir_dentry)); + fsstack_copy_attr_times(directory_inode, lower_dir); + fsstack_copy_inode_size(directory_inode, lower_dir); out_lock: - unlock_dir(lower_dir_dentry); + inode_unlock(lower_dir); return inode; } @@ -430,28 +425,28 @@ static int ecryptfs_link(struct dentry *old_dentry, struct inode *dir, { struct dentry *lower_old_dentry; struct dentry *lower_new_dentry; - struct dentry *lower_dir_dentry; + struct inode *lower_dir; u64 file_size_save; int rc; file_size_save = i_size_read(d_inode(old_dentry)); lower_old_dentry = ecryptfs_dentry_to_lower(old_dentry); - lower_new_dentry = ecryptfs_dentry_to_lower(new_dentry); - lower_dir_dentry = lock_parent(lower_new_dentry); - rc = vfs_link(lower_old_dentry, &init_user_ns, - d_inode(lower_dir_dentry), lower_new_dentry, NULL); + rc = lock_parent(new_dentry, &lower_new_dentry, &lower_dir); + if (!rc) + rc = vfs_link(lower_old_dentry, &init_user_ns, lower_dir, + lower_new_dentry, NULL); if (rc || d_really_is_negative(lower_new_dentry)) goto out_lock; rc = ecryptfs_interpose(lower_new_dentry, new_dentry, dir->i_sb); if (rc) goto out_lock; - fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry)); - fsstack_copy_inode_size(dir, d_inode(lower_dir_dentry)); + fsstack_copy_attr_times(dir, lower_dir); + fsstack_copy_inode_size(dir, lower_dir); set_nlink(d_inode(old_dentry), ecryptfs_inode_to_lower(d_inode(old_dentry))->i_nlink); i_size_write(d_inode(new_dentry), file_size_save); out_lock: - unlock_dir(lower_dir_dentry); + inode_unlock(lower_dir); return rc; } @@ -466,13 +461,14 @@ static int ecryptfs_symlink(struct user_namespace *mnt_userns, { int rc; struct dentry *lower_dentry; - struct dentry *lower_dir_dentry; + struct inode *lower_dir; char *encoded_symname; size_t encoded_symlen; struct ecryptfs_mount_crypt_stat *mount_crypt_stat = NULL; - lower_dentry = ecryptfs_dentry_to_lower(dentry); - lower_dir_dentry = lock_parent(lower_dentry); + rc = lock_parent(dentry, &lower_dentry, &lower_dir); + if (rc) + goto out_lock; mount_crypt_stat = &ecryptfs_superblock_to_private( dir->i_sb)->mount_crypt_stat; rc = ecryptfs_encrypt_and_encode_filename(&encoded_symname, @@ -481,7 +477,7 @@ static int ecryptfs_symlink(struct user_namespace *mnt_userns, strlen(symname)); if (rc) goto out_lock; - rc = vfs_symlink(&init_user_ns, d_inode(lower_dir_dentry), lower_dentry, + rc = vfs_symlink(&init_user_ns, lower_dir, lower_dentry, encoded_symname); kfree(encoded_symname); if (rc || d_really_is_negative(lower_dentry)) @@ -489,10 +485,10 @@ static int ecryptfs_symlink(struct user_namespace *mnt_userns, rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb); if (rc) goto out_lock; - fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry)); - fsstack_copy_inode_size(dir, d_inode(lower_dir_dentry)); + fsstack_copy_attr_times(dir, lower_dir); + fsstack_copy_inode_size(dir, lower_dir); out_lock: - unlock_dir(lower_dir_dentry); + inode_unlock(lower_dir); if (d_really_is_negative(dentry)) d_drop(dentry); return rc; @@ -503,22 +499,22 @@ static int ecryptfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir, { int rc; struct dentry *lower_dentry; - struct dentry *lower_dir_dentry; + struct inode *lower_dir; - lower_dentry = ecryptfs_dentry_to_lower(dentry); - lower_dir_dentry = lock_parent(lower_dentry); - rc = vfs_mkdir(&init_user_ns, d_inode(lower_dir_dentry), lower_dentry, - mode); + rc = lock_parent(dentry, &lower_dentry, &lower_dir); + if (!rc) + rc = vfs_mkdir(&init_user_ns, lower_dir, + lower_dentry, mode); if (rc || d_really_is_negative(lower_dentry)) goto out; rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb); if (rc) goto out; - fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry)); - fsstack_copy_inode_size(dir, d_inode(lower_dir_dentry)); - set_nlink(dir, d_inode(lower_dir_dentry)->i_nlink); + fsstack_copy_attr_times(dir, lower_dir); + fsstack_copy_inode_size(dir, lower_dir); + set_nlink(dir, lower_dir->i_nlink); out: - unlock_dir(lower_dir_dentry); + inode_unlock(lower_dir); if (d_really_is_negative(dentry)) d_drop(dentry); return rc; @@ -527,29 +523,24 @@ static int ecryptfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir, static int ecryptfs_rmdir(struct inode *dir, struct dentry *dentry) { struct dentry *lower_dentry; - struct dentry *lower_dir_dentry; - struct inode *lower_dir_inode; + struct inode *lower_dir; int rc; - lower_dentry = ecryptfs_dentry_to_lower(dentry); - lower_dir_dentry = ecryptfs_dentry_to_lower(dentry->d_parent); - lower_dir_inode = d_inode(lower_dir_dentry); - - inode_lock_nested(lower_dir_inode, I_MUTEX_PARENT); + rc = lock_parent(dentry, &lower_dentry, &lower_dir); dget(lower_dentry); // don't even try to make the lower negative - if (lower_dentry->d_parent != lower_dir_dentry) - rc = -EINVAL; - else if (d_unhashed(lower_dentry)) - rc = -EINVAL; - else - rc = vfs_rmdir(&init_user_ns, lower_dir_inode, lower_dentry); + if (!rc) { + if (d_unhashed(lower_dentry)) + rc = -EINVAL; + else + rc = vfs_rmdir(&init_user_ns, lower_dir, lower_dentry); + } if (!rc) { clear_nlink(d_inode(dentry)); - fsstack_copy_attr_times(dir, lower_dir_inode); - set_nlink(dir, lower_dir_inode->i_nlink); + fsstack_copy_attr_times(dir, lower_dir); + set_nlink(dir, lower_dir->i_nlink); } dput(lower_dentry); - inode_unlock(lower_dir_inode); + inode_unlock(lower_dir); if (!rc) d_drop(dentry); return rc; @@ -561,21 +552,21 @@ ecryptfs_mknod(struct user_namespace *mnt_userns, struct inode *dir, { int rc; struct dentry *lower_dentry; - struct dentry *lower_dir_dentry; + struct inode *lower_dir; - lower_dentry = ecryptfs_dentry_to_lower(dentry); - lower_dir_dentry = lock_parent(lower_dentry); - rc = vfs_mknod(&init_user_ns, d_inode(lower_dir_dentry), lower_dentry, - mode, dev); + rc = lock_parent(dentry, &lower_dentry, &lower_dir); + if (!rc) + rc = vfs_mknod(&init_user_ns, lower_dir, + lower_dentry, mode, dev); if (rc || d_really_is_negative(lower_dentry)) goto out; rc = ecryptfs_interpose(lower_dentry, dentry, dir->i_sb); if (rc) goto out; - fsstack_copy_attr_times(dir, d_inode(lower_dir_dentry)); - fsstack_copy_inode_size(dir, d_inode(lower_dir_dentry)); + fsstack_copy_attr_times(dir, lower_dir); + fsstack_copy_inode_size(dir, lower_dir); out: - unlock_dir(lower_dir_dentry); + inode_unlock(lower_dir); if (d_really_is_negative(dentry)) d_drop(dentry); return rc;