[PATCH v5 21/30] ovl: implement get acl method

[PATCH v5 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
    
    /* v5 */
    Miklos Szeredi <miklos@szeredi.hu>:
    - Consolidate get acl methods into one.
    - Add comment why we temporarily implement two instead of one because we are
      skipping permission checks on accident for a long time.

 fs/overlayfs/dir.c       |   3 +-
 fs/overlayfs/inode.c     | 109 ++++++++++++++++++++++++++++-----------
 fs/overlayfs/overlayfs.h |  17 +++++-
 3 files changed, 95 insertions(+), 34 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 6eefd8b7868e..74edbd1c1159 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"
 
 
@@ -460,7 +462,7 @@ 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,
+static void ovl_idmap_posix_acl(const struct inode *realinode,
 				struct user_namespace *mnt_userns,
 				struct posix_acl *acl)
 {
@@ -484,6 +486,64 @@ static void ovl_idmap_posix_acl(struct inode *realinode,
 	}
 }
 
+/*
+ * The @noperm argument is used to skip permission checking and is a temporary
+ * measure. Quoting Miklos from an earlier discussion:
+ *
+ * > So there are two paths to getting an acl:
+ * > 1) permission checking and 2) retrieving the value via getxattr(2).
+ * > This is a similar situation as reading a symlink vs. following it.
+ * > When following a symlink overlayfs always reads the link on the
+ * > underlying fs just as if it was a readlink(2) call, calling
+ * > security_inode_readlink() instead of security_inode_follow_link().
+ * > This is logical: we are reading the link from the underlying storage,
+ * > and following it on overlayfs.
+ * >
+ * > Applying the same logic to acl: we do need to call the
+ * > security_inode_getxattr() on the underlying fs, even if just want to
+ * > check permissions on overlay. This is currently not done, which is an
+ * > inconsistency.
+ * >
+ * > Maybe adding the check to ovl_get_acl() is the right way to go, but
+ * > I'm a little afraid of a performance regression.  Will look into that.
+ *
+ * Until we have made a decision allow this helper to take the @noperm
+ * argument. We should hopefully be able to remove it soon.
+ */
+static struct posix_acl *ovl_get_acl_path(const struct path *path,
+					  const char *acl_name, bool noperm)
+{
+	struct posix_acl *real_acl, *clone;
+	struct user_namespace *mnt_userns;
+	struct inode *realinode = d_inode(path->dentry);
+
+	mnt_userns = mnt_user_ns(path->mnt);
+
+	if (noperm)
+		real_acl = get_inode_acl(realinode, posix_acl_type(acl_name));
+	else
+		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);
+	posix_acl_release(real_acl); /* release original acl */
+	if (!clone)
+		return ERR_PTR(-ENOMEM);
+
+	ovl_idmap_posix_acl(realinode, mnt_userns, clone);
+	return clone;
+}
+
 /*
  * When the relevant layer is an idmapped mount we need to take the idmapping
  * of the layer into account and translate any ACL_{GROUP,USER} values
@@ -495,10 +555,12 @@ 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 *do_ovl_get_acl(struct user_namespace *mnt_userns,
+				 struct inode *inode, int type,
+				 bool rcu, bool noperm)
 {
 	struct inode *realinode = ovl_inode_real(inode);
-	struct posix_acl *acl, *clone;
+	struct posix_acl *acl;
 	struct path realpath;
 
 	if (!IS_POSIXACL(realinode))
@@ -512,40 +574,23 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu)
 	}
 
 	if (rcu) {
+		/*
+		 * If the layer is idmapped drop out of RCU path walk
+		 * so we can clone the ACLs.
+		 */
+		if (is_idmapped_mnt(realpath.mnt))
+			return ERR_PTR(-ECHILD);
+
 		acl = get_cached_acl_rcu(realinode, type);
 	} else {
 		const struct cred *old_cred;
 
 		old_cred = ovl_override_creds(inode->i_sb);
-		acl = get_inode_acl(realinode, type);
+		acl = ovl_get_acl_path(&realpath, posix_acl_xattr_name(type), noperm);
 		revert_creds(old_cred);
 	}
-	/*
-	 * If there are no POSIX ACLs, or we encountered an error,
-	 * or the layer isn't idmapped we don't need to do anything.
-	 */
-	if (!is_idmapped_mnt(realpath.mnt) || IS_ERR_OR_NULL(acl))
-		return acl;
-
-	/*
-	 * We only get here if the layer is idmapped. So drop out of RCU path
-	 * walk so we can clone the ACLs. There's no need to release the ACLs
-	 * since get_cached_acl_rcu() doesn't take a reference on the ACLs.
-	 */
-	if (rcu)
-		return ERR_PTR(-ECHILD);
 
-	clone = posix_acl_clone(acl, GFP_KERNEL);
-	if (!clone)
-		clone = ERR_PTR(-ENOMEM);
-	else
-		ovl_idmap_posix_acl(realinode, mnt_user_ns(realpath.mnt), clone);
-	/*
-	 * Since we're not in RCU path walk we always need to release the
-	 * original ACLs.
-	 */
-	posix_acl_release(acl);
-	return clone;
+	return acl;
 }
 #endif
 
@@ -721,7 +766,8 @@ 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 +787,8 @@ 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 eee8f08d32b6..d334977030c8 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -594,9 +594,22 @@ 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 *do_ovl_get_acl(struct user_namespace *mnt_userns,
+				 struct inode *inode, int type,
+				 bool rcu, bool noperm);
+static inline struct posix_acl *ovl_get_inode_acl(struct inode *inode, int type,
+						  bool rcu)
+{
+	return do_ovl_get_acl(&init_user_ns, inode, type, rcu, true);
+}
+static inline struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
+					    struct dentry *dentry, int type)
+{
+	return do_ovl_get_acl(mnt_userns, d_inode(dentry), type, false, false);
+}
 #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 v5 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>
Acked-by: Miklos Szeredi <miklos@szeredi.hu>
---

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
    
    /* v5 */
    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 74edbd1c1159..304a6dbb852a 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -592,6 +592,98 @@ struct posix_acl *do_ovl_get_acl(struct user_namespace *mnt_userns,
 
 	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)
@@ -768,6 +860,7 @@ 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,
@@ -789,6 +882,7 @@ 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 d334977030c8..ab5061c9aa2a 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)
@@ -607,9 +621,12 @@ static inline struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
 {
 	return do_ovl_get_acl(mnt_userns, d_inode(dentry), type, false, false);
 }
+int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
+		struct posix_acl *acl, int type);
 #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

[PATCH v5 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>
Acked-by: Miklos Szeredi <miklos@szeredi.hu>
---

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
    
    /* v5 */
    unchanged

 fs/overlayfs/copy_up.c   | 38 ++++++++++++++++++++++++++++++++++++++
 fs/overlayfs/dir.c       | 20 ++------------------
 fs/overlayfs/inode.c     |  4 ++--
 fs/overlayfs/overlayfs.h |  8 ++++++++
 fs/overlayfs/super.c     |  6 ++----
 fs/xattr.c               |  6 ------
 include/linux/xattr.h    |  6 ++++++
 7 files changed, 58 insertions(+), 30 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index f436d8847f08..6e4e65ee050d 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, false);
+	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, const struct path *oldpath, struct dentry *new)
 {
 	struct dentry *old = oldpath->dentry;
@@ -93,6 +122,15 @@ int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct de
 			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 304a6dbb852a..77a77fd7a77b 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -510,8 +510,8 @@ static void ovl_idmap_posix_acl(const struct inode *realinode,
  * Until we have made a decision allow this helper to take the @noperm
  * argument. We should hopefully be able to remove it soon.
  */
-static struct posix_acl *ovl_get_acl_path(const struct path *path,
-					  const char *acl_name, bool noperm)
+struct posix_acl *ovl_get_acl_path(const struct path *path,
+				   const char *acl_name, bool noperm)
 {
 	struct posix_acl *real_acl, *clone;
 	struct user_namespace *mnt_userns;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index ab5061c9aa2a..480e6aabef27 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -623,10 +623,18 @@ static inline struct posix_acl *ovl_get_acl(struct user_namespace *mnt_userns,
 }
 int ovl_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
 		struct posix_acl *acl, int type);
+struct posix_acl *ovl_get_acl_path(const struct path *path,
+				   const char *acl_name, bool noperm);
 #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,
+						 bool noperm)
+{
+	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 a29a8afe9b26..5c1b7971a9b3 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -813,13 +813,11 @@ 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 31b5ac65ca34..9ed9eea4d1b9 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -299,12 +299,6 @@ __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

[PATCH v5 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
    
    /* v5 */
    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 5c1b7971a9b3..2addafe4e14a 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -999,83 +999,6 @@ 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)
@@ -1108,22 +1031,6 @@ 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,
@@ -1144,8 +1051,8 @@ 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,
@@ -1154,8 +1061,8 @@ 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