[PATCH v4 21/30] ovl: implement get acl method

[PATCH v4 21/30] ovl: implement get acl method

[Christian Brauner]

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].

In order to build a type safe posix api around get and set acl we need
all filesystem to implement get and set acl.

Now that we have added get and set acl inode operations that allow easy
access to the dentry we give overlayfs it's own get and set acl inode
operations.

Since overlayfs is a stacking filesystem it will use the newly added
posix acl api when retrieving posix acls from the relevant layer.

Since overlayfs can also be mounted on top of idmapped layers. If
idmapped layers are used overlayfs must take the layer's idmapping into
account after it retrieved the posix acls from the relevant layer.

Note, until the vfs has been switched to the new posix acl api this
patch is a non-functional change.

Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---

Notes:
    /* v2 */
    Miklos Szeredi <mszeredi@redhat.com>
    - Use IS_ERR_OR_NULL() macro.
    
    /* v3 */
    unchanged
    
    /* v4 */
    unchanged

 fs/overlayfs/dir.c       |  3 +-
 fs/overlayfs/inode.c     | 61 ++++++++++++++++++++++++++++++++++++----
 fs/overlayfs/overlayfs.h | 10 +++++--
 3 files changed, 65 insertions(+), 9 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 7bece7010c00..eb49d5d7b56f 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -1311,7 +1311,8 @@ const struct inode_operations ovl_dir_inode_operations = {
 	.permission	= ovl_permission,
 	.getattr	= ovl_getattr,
 	.listxattr	= ovl_listxattr,
-	.get_inode_acl	= ovl_get_acl,
+	.get_inode_acl	= ovl_get_inode_acl,
+	.get_acl	= ovl_get_acl,
 	.update_time	= ovl_update_time,
 	.fileattr_get	= ovl_fileattr_get,
 	.fileattr_set	= ovl_fileattr_set,
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 9bc4582e956b..c25b4fd530db 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -14,6 +14,8 @@
 #include <linux/fileattr.h>
 #include <linux/security.h>
 #include <linux/namei.h>
+#include <linux/posix_acl.h>
+#include <linux/posix_acl_xattr.h>
 #include "overlayfs.h"
 
 
@@ -460,9 +462,9 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
  * of the POSIX ACLs retrieved from the lower layer to this function to not
  * alter the POSIX ACLs for the underlying filesystem.
  */
-static void ovl_idmap_posix_acl(struct inode *realinode,
-				struct user_namespace *mnt_userns,
-				struct posix_acl *acl)
+void ovl_idmap_posix_acl(struct inode *realinode,
+			 struct user_namespace *mnt_userns,
+			 struct posix_acl *acl)
 {
 	struct user_namespace *fs_userns = i_user_ns(realinode);
 
@@ -495,7 +497,7 @@ static void ovl_idmap_posix_acl(struct inode *realinode,
  *
  * This is obviously only relevant when idmapped layers are used.
  */
-struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu)
+struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type, bool rcu)
 {
 	struct inode *realinode = ovl_inode_real(inode);
 	struct posix_acl *acl, *clone;
@@ -547,6 +549,51 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu)
 	posix_acl_release(acl);
 	return clone;
 }
+
+static struct posix_acl *ovl_get_acl_path(const struct path *path,
+					  const char *acl_name)
+{
+	struct posix_acl *real_acl, *clone;
+	struct user_namespace *mnt_userns;
+
+	mnt_userns = mnt_user_ns(path->mnt);
+
+	real_acl = vfs_get_acl(mnt_userns, path->dentry, acl_name);
+	if (IS_ERR_OR_NULL(real_acl))
+		return real_acl;
+
+	if (!is_idmapped_mnt(path->mnt))
+		return real_acl;
+
+	/*
+        * We cannot alter the ACLs returned from the relevant layer as that
+        * would alter the cached values filesystem wide for the lower
+        * filesystem. Instead we can clone the ACLs and then apply the
+        * relevant idmapping of the layer.
+        */
+	clone = posix_acl_clone(real_acl, GFP_KERNEL);
+	if (clone)
+		ovl_idmap_posix_acl(d_inode(path->dentry), mnt_userns, clone);
+	else
+		clone = ERR_PTR(-ENOMEM);
+	/* Drop reference to original posix acls. */
+	posix_acl_release(real_acl);
+	return clone;
+}
+
+struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
+			      struct dentry *dentry, int type)
+{
+	struct posix_acl *acl = NULL;
+	const struct cred *old_cred;
+	struct path realpath;
+
+	ovl_path_real(dentry, &realpath);
+	old_cred = ovl_override_creds(dentry->d_sb);
+	acl = ovl_get_acl_path(&realpath, posix_acl_xattr_name(type));
+	revert_creds(old_cred);
+	return acl;
+}
 #endif
 
 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
@@ -721,7 +768,8 @@ static const struct inode_operations ovl_file_inode_operations = {
 	.permission	= ovl_permission,
 	.getattr	= ovl_getattr,
 	.listxattr	= ovl_listxattr,
-	.get_inode_acl	= ovl_get_acl,
+	.get_inode_acl	= ovl_get_inode_acl,
+	.get_acl	= ovl_get_acl,
 	.update_time	= ovl_update_time,
 	.fiemap		= ovl_fiemap,
 	.fileattr_get	= ovl_fileattr_get,
@@ -741,7 +789,8 @@ static const struct inode_operations ovl_special_inode_operations = {
 	.permission	= ovl_permission,
 	.getattr	= ovl_getattr,
 	.listxattr	= ovl_listxattr,
-	.get_inode_acl	= ovl_get_acl,
+	.get_inode_acl	= ovl_get_inode_acl,
+	.get_acl	= ovl_get_acl,
 	.update_time	= ovl_update_time,
 };
 
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index ee93c825b06b..68a3030332e9 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -592,9 +592,15 @@ int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
 
 #ifdef CONFIG_FS_POSIX_ACL
-struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu);
+struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type, bool rcu);
+struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
+			      struct dentry *dentry, int type);
+void ovl_idmap_posix_acl(struct inode *realinode,
+			 struct user_namespace *mnt_userns,
+			 struct posix_acl *acl);
 #else
-#define ovl_get_acl	NULL
+#define ovl_get_inode_acl	NULL
+#define ovl_get_acl		NULL
 #endif
 
 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);
-- 
2.34.1

[PATCH v4 22/30] ovl: implement set acl method

[Christian Brauner]

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].

In order to build a type safe posix api around get and set acl we need
all filesystem to implement get and set acl.

Now that we have added get and set acl inode operations that allow easy
access to the dentry we give overlayfs it's own get and set acl inode
operations.

The set acl inode operation is duplicates most of the ovl posix acl
xattr handler. The main difference being that the set acl inode
operation relies on the new posix acl api. Once the vfs has been
switched over the custom posix acl xattr handler will be removed
completely.

Note, until the vfs has been switched to the new posix acl api this
patch is a non-functional change.

Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---

Notes:
    /* v2 */
    Miklos Szeredi <miklos@szeredi.hu>:
    - split ovl_set_acl() into two functions
    - add comment about checking whether copy up is even necessary
    
    /* v3 */
    unchanged
    
    /* v4 */
    unchanged

 fs/overlayfs/dir.c       |  1 +
 fs/overlayfs/inode.c     | 94 ++++++++++++++++++++++++++++++++++++++++
 fs/overlayfs/overlayfs.h | 17 ++++++++
 3 files changed, 112 insertions(+)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index eb49d5d7b56f..0e817ebce92c 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -1313,6 +1313,7 @@ const struct inode_operations ovl_dir_inode_operations = {
 	.listxattr	= ovl_listxattr,
 	.get_inode_acl	= ovl_get_inode_acl,
 	.get_acl	= ovl_get_acl,
+	.set_acl	= ovl_set_acl,
 	.update_time	= ovl_update_time,
 	.fileattr_get	= ovl_fileattr_get,
 	.fileattr_set	= ovl_fileattr_set,
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index c25b4fd530db..d32bfa87cd79 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -594,6 +594,98 @@ struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
 	revert_creds(old_cred);
 	return acl;
 }
+
+static int ovl_set_or_remove_acl(struct dentry *dentry, struct inode *inode,
+				 struct posix_acl *acl, int type)
+{
+	int err;
+	struct path realpath;
+	const char *acl_name;
+	const struct cred *old_cred;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	struct dentry *upperdentry = ovl_dentry_upper(dentry);
+	struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
+
+	err = ovl_want_write(dentry);
+	if (err)
+		return err;
+
+	/*
+	 * If ACL is to be removed from a lower file, check if it exists in
+	 * the first place before copying it up.
+	 */
+	acl_name = posix_acl_xattr_name(type);
+	if (!acl && !upperdentry) {
+		struct posix_acl *real_acl;
+
+		ovl_path_lower(dentry, &realpath);
+		old_cred = ovl_override_creds(dentry->d_sb);
+		real_acl = vfs_get_acl(mnt_user_ns(realpath.mnt), realdentry,
+				       acl_name);
+		revert_creds(old_cred);
+		posix_acl_release(real_acl);
+		if (IS_ERR(real_acl)) {
+			err = PTR_ERR(real_acl);
+			goto out_drop_write;
+		}
+	}
+
+	if (!upperdentry) {
+		err = ovl_copy_up(dentry);
+		if (err)
+			goto out_drop_write;
+
+		realdentry = ovl_dentry_upper(dentry);
+	}
+
+	old_cred = ovl_override_creds(dentry->d_sb);
+	if (acl)
+		err = ovl_do_set_acl(ofs, realdentry, acl_name, acl);
+	else
+		err = ovl_do_remove_acl(ofs, realdentry, acl_name);
+	revert_creds(old_cred);
+
+	/* copy c/mtime */
+	ovl_copyattr(inode);
+
+out_drop_write:
+	ovl_drop_write(dentry);
+	return err;
+}
+
+int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct posix_acl *acl, int type)
+{
+	int err;
+	struct inode *inode = d_inode(dentry);
+	struct dentry *workdir = ovl_workdir(dentry);
+	struct inode *realinode = ovl_inode_real(inode);
+
+	if (!IS_POSIXACL(d_inode(workdir)))
+		return -EOPNOTSUPP;
+	if (!realinode->i_op->set_acl)
+		return -EOPNOTSUPP;
+	if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
+		return acl ? -EACCES : 0;
+	if (!inode_owner_or_capable(&init_user_ns, inode))
+		return -EPERM;
+
+	/*
+	 * Check if sgid bit needs to be cleared (actual setacl operation will
+	 * be done with mounter's capabilities and so that won't do it for us).
+	 */
+	if (unlikely(inode->i_mode & S_ISGID) && type == ACL_TYPE_ACCESS &&
+	    !in_group_p(inode->i_gid) &&
+	    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID)) {
+		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
+
+		err = ovl_setattr(&init_user_ns, dentry, &iattr);
+		if (err)
+			return err;
+	}
+
+	return ovl_set_or_remove_acl(dentry, inode, acl, type);
+}
 #endif
 
 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
@@ -770,6 +862,7 @@ static const struct inode_operations ovl_file_inode_operations = {
 	.listxattr	= ovl_listxattr,
 	.get_inode_acl	= ovl_get_inode_acl,
 	.get_acl	= ovl_get_acl,
+	.set_acl	= ovl_set_acl,
 	.update_time	= ovl_update_time,
 	.fiemap		= ovl_fiemap,
 	.fileattr_get	= ovl_fileattr_get,
@@ -791,6 +884,7 @@ static const struct inode_operations ovl_special_inode_operations = {
 	.listxattr	= ovl_listxattr,
 	.get_inode_acl	= ovl_get_inode_acl,
 	.get_acl	= ovl_get_acl,
+	.set_acl	= ovl_set_acl,
 	.update_time	= ovl_update_time,
 };
 
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 68a3030332e9..b2645baeba2f 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -8,6 +8,8 @@
 #include <linux/uuid.h>
 #include <linux/fs.h>
 #include <linux/namei.h>
+#include <linux/posix_acl.h>
+#include <linux/posix_acl_xattr.h>
 #include "ovl_entry.h"
 
 #undef pr_fmt
@@ -278,6 +280,18 @@ static inline int ovl_removexattr(struct ovl_fs *ofs, struct dentry *dentry,
 	return ovl_do_removexattr(ofs, dentry, ovl_xattr(ofs, ox));
 }
 
+static inline int ovl_do_set_acl(struct ovl_fs *ofs, struct dentry *dentry,
+				 const char *acl_name, struct posix_acl *acl)
+{
+	return vfs_set_acl(ovl_upper_mnt_userns(ofs), dentry, acl_name, acl);
+}
+
+static inline int ovl_do_remove_acl(struct ovl_fs *ofs, struct dentry *dentry,
+				    const char *acl_name)
+{
+	return vfs_remove_acl(ovl_upper_mnt_userns(ofs), dentry, acl_name);
+}
+
 static inline int ovl_do_rename(struct ovl_fs *ofs, struct inode *olddir,
 				struct dentry *olddentry, struct inode *newdir,
 				struct dentry *newdentry, unsigned int flags)
@@ -595,12 +609,15 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
 struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type, bool rcu);
 struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
 			      struct dentry *dentry, int type);
+int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct posix_acl *acl, int type);
 void ovl_idmap_posix_acl(struct inode *realinode,
 			 struct user_namespace *mnt_userns,
 			 struct posix_acl *acl);
 #else
 #define ovl_get_inode_acl	NULL
 #define ovl_get_acl		NULL
+#define ovl_set_acl		NULL
 #endif
 
 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);
-- 
2.34.1

Re: [PATCH v4 22/30] ovl: implement set acl method

[Miklos Szeredi]

On Thu, 29 Sept 2022 at 17:31, Christian Brauner <brauner@kernel.org> wrote:
>
> 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].
>
> In order to build a type safe posix api around get and set acl we need
> all filesystem to implement get and set acl.
>
> Now that we have added get and set acl inode operations that allow easy
> access to the dentry we give overlayfs it's own get and set acl inode
> operations.
>
> The set acl inode operation is duplicates most of the ovl posix acl
> xattr handler. The main difference being that the set acl inode
> operation relies on the new posix acl api. Once the vfs has been
> switched over the custom posix acl xattr handler will be removed
> completely.
>
> Note, until the vfs has been switched to the new posix acl api this
> patch is a non-functional change.
>
> Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

Acked-by: Miklos Szeredi <mszeredi@redhat.com>

Thanks,
Miklos

[PATCH v4 23/30] ovl: use posix acl api

[Christian Brauner]

Now that posix acls have a proper api us it to copy them.

All filesystems that can serve as lower or upper layers for overlayfs
have gained support for the new posix acl api in previous patches.
So switch all internal overlayfs codepaths for copying posix acls to the
new posix acl api.

Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---

Notes:
    /* v2 */
    Miklos Szeredi <miklos@szeredi.hu>:
    - Move ovl_copy_acl() from util.c to copy_up.c
    - Unconditionally clone posix acls
    
    /* v3 */
    unchanged
    
    /* v4 */
    unchanged

 fs/overlayfs/copy_up.c   | 38 ++++++++++++++++++++++++++++++++++++++
 fs/overlayfs/dir.c       | 20 ++------------------
 fs/overlayfs/inode.c     |  4 ++--
 fs/overlayfs/overlayfs.h |  7 +++++++
 fs/overlayfs/super.c     |  6 ++----
 fs/xattr.c               |  6 ------
 include/linux/xattr.h    |  6 ++++++
 7 files changed, 57 insertions(+), 30 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index fdde6c56cc3d..f2e36c841d6f 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -44,6 +44,35 @@ static bool ovl_must_copy_xattr(const char *name)
 	       !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN);
 }
 
+static int ovl_copy_acl(struct ovl_fs *ofs, const struct path *path,
+			struct dentry *dentry, const char *acl_name)
+{
+	int err;
+	struct posix_acl *clone, *real_acl = NULL;
+
+	real_acl = ovl_get_acl_path(path, acl_name);
+	if (!real_acl)
+		return 0;
+
+	if (IS_ERR(real_acl)) {
+		err = PTR_ERR(real_acl);
+		if (err == -ENODATA || err == -EOPNOTSUPP)
+			return 0;
+		return err;
+	}
+
+	clone = posix_acl_clone(real_acl, GFP_KERNEL);
+	posix_acl_release(real_acl); /* release original acl */
+	if (!clone)
+		return -ENOMEM;
+
+	err = ovl_do_set_acl(ofs, dentry, acl_name, clone);
+
+	/* release cloned acl */
+	posix_acl_release(clone);
+	return err;
+}
+
 int ovl_copy_xattr(struct super_block *sb, struct path *oldpath, struct dentry *new)
 {
 	struct dentry *old = oldpath->dentry;
@@ -93,6 +122,15 @@ int ovl_copy_xattr(struct super_block *sb, struct path *oldpath, struct dentry *
 			error = 0;
 			continue; /* Discard */
 		}
+
+		if (is_posix_acl_xattr(name)) {
+			error = ovl_copy_acl(OVL_FS(sb), oldpath, new, name);
+			if (!error)
+				continue;
+			/* POSIX ACLs must be copied. */
+			break;
+		}
+
 retry:
 		size = ovl_do_getxattr(oldpath, name, value, value_size);
 		if (size == -ERANGE)
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 0e817ebce92c..cbb569d5d234 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -435,28 +435,12 @@ static struct dentry *ovl_clear_empty(struct dentry *dentry,
 }
 
 static int ovl_set_upper_acl(struct ovl_fs *ofs, struct dentry *upperdentry,
-			     const char *name, const struct posix_acl *acl)
+			     const char *acl_name, struct posix_acl *acl)
 {
-	void *buffer;
-	size_t size;
-	int err;
-
 	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
 		return 0;
 
-	size = posix_acl_xattr_size(acl->a_count);
-	buffer = kmalloc(size, GFP_KERNEL);
-	if (!buffer)
-		return -ENOMEM;
-
-	err = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
-	if (err < 0)
-		goto out_free;
-
-	err = ovl_do_setxattr(ofs, upperdentry, name, buffer, size, XATTR_CREATE);
-out_free:
-	kfree(buffer);
-	return err;
+	return ovl_do_set_acl(ofs, upperdentry, acl_name, acl);
 }
 
 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index d32bfa87cd79..db3d41d1c69e 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -550,8 +550,8 @@ struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type, bool rcu)
 	return clone;
 }
 
-static struct posix_acl *ovl_get_acl_path(const struct path *path,
-					  const char *acl_name)
+struct posix_acl *ovl_get_acl_path(const struct path *path,
+				   const char *acl_name)
 {
 	struct posix_acl *real_acl, *clone;
 	struct user_namespace *mnt_userns;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index b2645baeba2f..f3b6d6625604 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -614,10 +614,17 @@ int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 void ovl_idmap_posix_acl(struct inode *realinode,
 			 struct user_namespace *mnt_userns,
 			 struct posix_acl *acl);
+struct posix_acl *ovl_get_acl_path(const struct path *path,
+				   const char *acl_name);
 #else
 #define ovl_get_inode_acl	NULL
 #define ovl_get_acl		NULL
 #define ovl_set_acl		NULL
+static inline struct posix_acl *ovl_get_acl_path(const struct path *path,
+						 const char *acl_name)
+{
+	return NULL;
+}
 #endif
 
 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 5da771b218d1..8a13319db1d3 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -812,13 +812,11 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 		 * allowed as upper are limited to "normal" ones, where checking
 		 * for the above two errors is sufficient.
 		 */
-		err = ovl_do_removexattr(ofs, work,
-					 XATTR_NAME_POSIX_ACL_DEFAULT);
+		err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_DEFAULT);
 		if (err && err != -ENODATA && err != -EOPNOTSUPP)
 			goto out_dput;
 
-		err = ovl_do_removexattr(ofs, work,
-					 XATTR_NAME_POSIX_ACL_ACCESS);
+		err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_ACCESS);
 		if (err && err != -ENODATA && err != -EOPNOTSUPP)
 			goto out_dput;
 
diff --git a/fs/xattr.c b/fs/xattr.c
index 57148c207545..6303f1c62796 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -296,12 +296,6 @@ __vfs_setxattr_locked(struct user_namespace *mnt_userns, struct dentry *dentry,
 }
 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
 
-static inline bool is_posix_acl_xattr(const char *name)
-{
-	return (strcmp(name, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
-	       (strcmp(name, XATTR_NAME_POSIX_ACL_DEFAULT) == 0);
-}
-
 int
 vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 	     const char *name, const void *value, size_t size, int flags)
diff --git a/include/linux/xattr.h b/include/linux/xattr.h
index 4c379d23ec6e..c5238744bab9 100644
--- a/include/linux/xattr.h
+++ b/include/linux/xattr.h
@@ -22,6 +22,12 @@
 struct inode;
 struct dentry;
 
+static inline bool is_posix_acl_xattr(const char *name)
+{
+	return (strcmp(name, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
+	       (strcmp(name, XATTR_NAME_POSIX_ACL_DEFAULT) == 0);
+}
+
 /*
  * struct xattr_handler: When @name is set, match attributes with exactly that
  * name.  When @prefix is set instead, match attributes with that prefix and
-- 
2.34.1

Re: [PATCH v4 23/30] ovl: use posix acl api

[Miklos Szeredi]

On Thu, 29 Sept 2022 at 17:31, Christian Brauner <brauner@kernel.org> wrote:
>
> Now that posix acls have a proper api us it to copy them.
>
> All filesystems that can serve as lower or upper layers for overlayfs
> have gained support for the new posix acl api in previous patches.
> So switch all internal overlayfs codepaths for copying posix acls to the
> new posix acl api.
>
> Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

Acked-by: Miklos Szeredi <mszeredi@redhat.com>

Thanks,
Miklos

[PATCH v4 27/30] ovl: use stub posix acl handlers

[Christian Brauner]

Now that ovl supports the get and set acl inode operations and the vfs
has been switched to the new posi api, ovl can simply rely on the stub
posix acl handlers. The custom xattr handlers and associated unused
helpers can be removed.

Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---

Notes:
    /* v2 */
    unchanged
    
    /* v3 */
    unchanged
    
    /* v4 */
    unchanged

 fs/overlayfs/super.c | 101 ++-----------------------------------------
 1 file changed, 4 insertions(+), 97 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 8a13319db1d3..0c7ae79b10b1 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -998,83 +998,6 @@ static unsigned int ovl_split_lowerdirs(char *str)
 	return ctr;
 }
 
-static int __maybe_unused
-ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
-			struct dentry *dentry, struct inode *inode,
-			const char *name, void *buffer, size_t size)
-{
-	return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
-}
-
-static int __maybe_unused
-ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
-			struct user_namespace *mnt_userns,
-			struct dentry *dentry, struct inode *inode,
-			const char *name, const void *value,
-			size_t size, int flags)
-{
-	struct dentry *workdir = ovl_workdir(dentry);
-	struct inode *realinode = ovl_inode_real(inode);
-	struct posix_acl *acl = NULL;
-	int err;
-
-	/* Check that everything is OK before copy-up */
-	if (value) {
-		/* The above comment can be understood in two ways:
-		 *
-		 * 1. We just want to check whether the basic POSIX ACL format
-		 *    is ok. For example, if the header is correct and the size
-		 *    is sane.
-		 * 2. We want to know whether the ACL_{GROUP,USER} entries can
-		 *    be mapped according to the underlying filesystem.
-		 *
-		 * Currently, we only check 1. If we wanted to check 2. we
-		 * would need to pass the mnt_userns and the fs_userns of the
-		 * underlying filesystem. But frankly, I think checking 1. is
-		 * enough to start the copy-up.
-		 */
-		acl = vfs_set_acl_prepare(&init_user_ns, &init_user_ns, value, size);
-		if (IS_ERR(acl))
-			return PTR_ERR(acl);
-	}
-	err = -EOPNOTSUPP;
-	if (!IS_POSIXACL(d_inode(workdir)))
-		goto out_acl_release;
-	if (!realinode->i_op->set_acl)
-		goto out_acl_release;
-	if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
-		err = acl ? -EACCES : 0;
-		goto out_acl_release;
-	}
-	err = -EPERM;
-	if (!inode_owner_or_capable(&init_user_ns, inode))
-		goto out_acl_release;
-
-	posix_acl_release(acl);
-
-	/*
-	 * Check if sgid bit needs to be cleared (actual setacl operation will
-	 * be done with mounter's capabilities and so that won't do it for us).
-	 */
-	if (unlikely(inode->i_mode & S_ISGID) &&
-	    handler->flags == ACL_TYPE_ACCESS &&
-	    !in_group_p(inode->i_gid) &&
-	    !capable_wrt_inode_uidgid(&init_user_ns, inode, CAP_FSETID)) {
-		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
-
-		err = ovl_setattr(&init_user_ns, dentry, &iattr);
-		if (err)
-			return err;
-	}
-
-	err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
-	return err;
-
-out_acl_release:
-	posix_acl_release(acl);
-	return err;
-}
-
 static int ovl_own_xattr_get(const struct xattr_handler *handler,
 			     struct dentry *dentry, struct inode *inode,
 			     const char *name, void *buffer, size_t size)
@@ -1107,22 +1030,6 @@ static int ovl_other_xattr_set(const struct xattr_handler *handler,
 	return ovl_xattr_set(dentry, inode, name, value, size, flags);
 }
 
-static const struct xattr_handler __maybe_unused
-ovl_posix_acl_access_xattr_handler = {
-	.name = XATTR_NAME_POSIX_ACL_ACCESS,
-	.flags = ACL_TYPE_ACCESS,
-	.get = ovl_posix_acl_xattr_get,
-	.set = ovl_posix_acl_xattr_set,
-};
-
-static const struct xattr_handler __maybe_unused
-ovl_posix_acl_default_xattr_handler = {
-	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
-	.flags = ACL_TYPE_DEFAULT,
-	.get = ovl_posix_acl_xattr_get,
-	.set = ovl_posix_acl_xattr_set,
-};
-
 static const struct xattr_handler ovl_own_trusted_xattr_handler = {
 	.prefix	= OVL_XATTR_TRUSTED_PREFIX,
 	.get = ovl_own_xattr_get,
@@ -1143,8 +1050,8 @@ static const struct xattr_handler ovl_other_xattr_handler = {
 
 static const struct xattr_handler *ovl_trusted_xattr_handlers[] = {
 #ifdef CONFIG_FS_POSIX_ACL
-	&ovl_posix_acl_access_xattr_handler,
-	&ovl_posix_acl_default_xattr_handler,
+	&posix_acl_access_xattr_handler,
+	&posix_acl_default_xattr_handler,
 #endif
 	&ovl_own_trusted_xattr_handler,
 	&ovl_other_xattr_handler,
@@ -1153,8 +1060,8 @@ static const struct xattr_handler *ovl_trusted_xattr_handlers[] = {
 
 static const struct xattr_handler *ovl_user_xattr_handlers[] = {
 #ifdef CONFIG_FS_POSIX_ACL
-	&ovl_posix_acl_access_xattr_handler,
-	&ovl_posix_acl_default_xattr_handler,
+	&posix_acl_access_xattr_handler,
+	&posix_acl_default_xattr_handler,
 #endif
 	&ovl_own_user_xattr_handler,
 	&ovl_other_xattr_handler,
-- 
2.34.1