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/nfs/nfs3_fs.h | 2 +- fs/nfs/nfs3acl.c | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-) (limited to 'fs/nfs') diff --git a/fs/nfs/nfs3_fs.h b/fs/nfs/nfs3_fs.h index 03a4e679fd99..df9ca56db347 100644 --- a/fs/nfs/nfs3_fs.h +++ b/fs/nfs/nfs3_fs.h @@ -12,7 +12,7 @@ */ #ifdef CONFIG_NFS_V3_ACL extern struct posix_acl *nfs3_get_acl(struct inode *inode, int type, bool rcu); -extern int nfs3_set_acl(struct user_namespace *mnt_userns, struct inode *inode, +extern int nfs3_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, struct posix_acl *acl, int type); extern int nfs3_proc_setacls(struct inode *inode, struct posix_acl *acl, struct posix_acl *dfacl); diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c index 93de0b58647a..22890d97a9e4 100644 --- a/fs/nfs/nfs3acl.c +++ b/fs/nfs/nfs3acl.c @@ -255,10 +255,11 @@ int nfs3_proc_setacls(struct inode *inode, struct posix_acl *acl, } -int nfs3_set_acl(struct user_namespace *mnt_userns, struct inode *inode, +int nfs3_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, struct posix_acl *acl, int type) { struct posix_acl *orig = acl, *dfacl = NULL, *alloc; + struct inode *inode = d_inode(dentry); int status; if (S_ISDIR(inode->i_mode)) { -- cgit 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/nfs/nfs3acl.c | 6 +++--- fs/nfs/nfs3proc.c | 4 ++-- 2 files changed, 5 insertions(+), 5 deletions(-) (limited to 'fs/nfs') diff --git a/fs/nfs/nfs3acl.c b/fs/nfs/nfs3acl.c index 22890d97a9e4..74d11e3c4205 100644 --- a/fs/nfs/nfs3acl.c +++ b/fs/nfs/nfs3acl.c @@ -265,14 +265,14 @@ int nfs3_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, if (S_ISDIR(inode->i_mode)) { switch(type) { case ACL_TYPE_ACCESS: - alloc = get_acl(inode, ACL_TYPE_DEFAULT); + alloc = get_inode_acl(inode, ACL_TYPE_DEFAULT); if (IS_ERR(alloc)) goto fail; dfacl = alloc; break; case ACL_TYPE_DEFAULT: - alloc = get_acl(inode, ACL_TYPE_ACCESS); + alloc = get_inode_acl(inode, ACL_TYPE_ACCESS); if (IS_ERR(alloc)) goto fail; dfacl = acl; @@ -313,7 +313,7 @@ nfs3_list_one_acl(struct inode *inode, int type, const char *name, void *data, struct posix_acl *acl; char *p = data + *result; - acl = get_acl(inode, type); + acl = get_inode_acl(inode, type); if (IS_ERR_OR_NULL(acl)) return 0; diff --git a/fs/nfs/nfs3proc.c b/fs/nfs/nfs3proc.c index 2e7579626cf0..4bf208a0a8e9 100644 --- a/fs/nfs/nfs3proc.c +++ b/fs/nfs/nfs3proc.c @@ -998,7 +998,7 @@ static const struct inode_operations nfs3_dir_inode_operations = { .setattr = nfs_setattr, #ifdef CONFIG_NFS_V3_ACL .listxattr = nfs3_listxattr, - .get_acl = nfs3_get_acl, + .get_inode_acl = nfs3_get_acl, .set_acl = nfs3_set_acl, #endif }; @@ -1009,7 +1009,7 @@ static const struct inode_operations nfs3_file_inode_operations = { .setattr = nfs_setattr, #ifdef CONFIG_NFS_V3_ACL .listxattr = nfs3_listxattr, - .get_acl = nfs3_get_acl, + .get_inode_acl = nfs3_get_acl, .set_acl = nfs3_set_acl, #endif }; -- cgit