From 138060ba92b3b0d77c8e6818d0f33398b23ea42e Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Fri, 23 Sep 2022 10:29:39 +0200 Subject: fs: pass dentry to set acl method The current way of setting and getting posix acls through the generic xattr interface is error prone and type unsafe. The vfs needs to interpret and fixup posix acls before storing or reporting it to userspace. Various hacks exist to make this work. The code is hard to understand and difficult to maintain in it's current form. Instead of making this work by hacking posix acls through xattr handlers we are building a dedicated posix acl api around the get and set inode operations. This removes a lot of hackiness and makes the codepaths easier to maintain. A lot of background can be found in [1]. Since some filesystem rely on the dentry being available to them when setting posix acls (e.g., 9p and cifs) they cannot rely on set acl inode operation. But since ->set_acl() is required in order to use the generic posix acl xattr handlers filesystems that do not implement this inode operation cannot use the handler and need to implement their own dedicated posix acl handlers. Update the ->set_acl() inode method to take a dentry argument. This allows all filesystems to rely on ->set_acl(). As far as I can tell all codepaths can be switched to rely on the dentry instead of just the inode. Note that the original motivation for passing the dentry separate from the inode instead of just the dentry in the xattr handlers was because of security modules that call security_d_instantiate(). This hook is called during d_instantiate_new(), d_add(), __d_instantiate_anon(), and d_splice_alias() to initialize the inode's security context and possibly to set security.* xattrs. Since this only affects security.* xattrs this is completely irrelevant for posix acls. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft) --- fs/ext4/acl.c | 3 ++- fs/ext4/acl.h | 2 +- fs/ext4/inode.c | 2 +- 3 files changed, 4 insertions(+), 3 deletions(-) (limited to 'fs/ext4') diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c index 57e82e25f8e2..a9f89539aeee 100644 --- a/fs/ext4/acl.c +++ b/fs/ext4/acl.c @@ -225,12 +225,13 @@ __ext4_set_acl(handle_t *handle, struct inode *inode, int type, } int -ext4_set_acl(struct user_namespace *mnt_userns, struct inode *inode, +ext4_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, struct posix_acl *acl, int type) { handle_t *handle; int error, credits, retries = 0; size_t acl_size = acl ? ext4_acl_size(acl->a_count) : 0; + struct inode *inode = d_inode(dentry); umode_t mode = inode->i_mode; int update_mode = 0; diff --git a/fs/ext4/acl.h b/fs/ext4/acl.h index 3219669732bf..09c4a8a3b716 100644 --- a/fs/ext4/acl.h +++ b/fs/ext4/acl.h @@ -56,7 +56,7 @@ static inline int ext4_acl_count(size_t size) /* acl.c */ struct posix_acl *ext4_get_acl(struct inode *inode, int type, bool rcu); -int ext4_set_acl(struct user_namespace *mnt_userns, struct inode *inode, +int ext4_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, struct posix_acl *acl, int type); extern int ext4_init_acl(handle_t *, struct inode *, struct inode *); diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 2b5ef1b64249..a8e12ce6673d 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5550,7 +5550,7 @@ out_mmap_sem: ext4_orphan_del(NULL, inode); if (!error && (ia_valid & ATTR_MODE)) - rc = posix_acl_chmod(mnt_userns, inode, inode->i_mode); + rc = posix_acl_chmod(mnt_userns, dentry, inode->i_mode); err_out: if (error) -- cgit v1.2.3 From cac2f8b8d8b50ef32b3e34f6dcbbf08937e4f616 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 22 Sep 2022 17:17:00 +0200 Subject: fs: rename current get acl method The current way of setting and getting posix acls through the generic xattr interface is error prone and type unsafe. The vfs needs to interpret and fixup posix acls before storing or reporting it to userspace. Various hacks exist to make this work. The code is hard to understand and difficult to maintain in it's current form. Instead of making this work by hacking posix acls through xattr handlers we are building a dedicated posix acl api around the get and set inode operations. This removes a lot of hackiness and makes the codepaths easier to maintain. A lot of background can be found in [1]. The current inode operation for getting posix acls takes an inode argument but various filesystems (e.g., 9p, cifs, overlayfs) need access to the dentry. In contrast to the ->set_acl() inode operation we cannot simply extend ->get_acl() to take a dentry argument. The ->get_acl() inode operation is called from: acl_permission_check() -> check_acl() -> get_acl() which is part of generic_permission() which in turn is part of inode_permission(). Both generic_permission() and inode_permission() are called in the ->permission() handler of various filesystems (e.g., overlayfs). So simply passing a dentry argument to ->get_acl() would amount to also having to pass a dentry argument to ->permission(). We should avoid this unnecessary change. So instead of extending the existing inode operation rename it from ->get_acl() to ->get_inode_acl() and add a ->get_acl() method later that passes a dentry argument and which filesystems that need access to the dentry can implement instead of ->get_inode_acl(). Filesystems like cifs which allow setting and getting posix acls but not using them for permission checking during lookup can simply not implement ->get_inode_acl(). This is intended to be a non-functional change. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Suggested-by/Inspired-by: Christoph Hellwig Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner (Microsoft) --- fs/ext4/file.c | 2 +- fs/ext4/ialloc.c | 2 +- fs/ext4/namei.c | 4 ++-- 3 files changed, 4 insertions(+), 4 deletions(-) (limited to 'fs/ext4') diff --git a/fs/ext4/file.c b/fs/ext4/file.c index a7a597c727e6..7ac0a81bd371 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -955,7 +955,7 @@ const struct inode_operations ext4_file_inode_operations = { .setattr = ext4_setattr, .getattr = ext4_file_getattr, .listxattr = ext4_listxattr, - .get_acl = ext4_get_acl, + .get_inode_acl = ext4_get_acl, .set_acl = ext4_set_acl, .fiemap = ext4_fiemap, .fileattr_get = ext4_fileattr_get, diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index e9bc46684106..67a257a69758 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -870,7 +870,7 @@ static int ext4_xattr_credits_for_new_inode(struct inode *dir, mode_t mode, struct super_block *sb = dir->i_sb; int nblocks = 0; #ifdef CONFIG_EXT4_FS_POSIX_ACL - struct posix_acl *p = get_acl(dir, ACL_TYPE_DEFAULT); + struct posix_acl *p = get_inode_acl(dir, ACL_TYPE_DEFAULT); if (IS_ERR(p)) return PTR_ERR(p); diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index d5daaf41e1fc..b8a91d74fdd1 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -4186,7 +4186,7 @@ const struct inode_operations ext4_dir_inode_operations = { .setattr = ext4_setattr, .getattr = ext4_getattr, .listxattr = ext4_listxattr, - .get_acl = ext4_get_acl, + .get_inode_acl = ext4_get_acl, .set_acl = ext4_set_acl, .fiemap = ext4_fiemap, .fileattr_get = ext4_fileattr_get, @@ -4197,6 +4197,6 @@ const struct inode_operations ext4_special_inode_operations = { .setattr = ext4_setattr, .getattr = ext4_getattr, .listxattr = ext4_listxattr, - .get_acl = ext4_get_acl, + .get_inode_acl = ext4_get_acl, .set_acl = ext4_set_acl, }; -- cgit v1.2.3