ovl: Move xattr support to new xattrs.c file

This moves the code from super.c and inode.c, and makes ovl_xattr_get/set()
static.

This is in preparation for doing more work on xattrs support.

Signed-off-by: Alexander Larsson <[e-mail]>
Reviewed-by: Amir Goldstein <[e-mail]>
Signed-off-by: Amir Goldstein <[e-mail]>

fs/overlayfs/Makefile

···
 obj-$(CONFIG_OVERLAY_FS) += overlay.o
 
 overlay-objs := super.o namei.o util.o inode.o file.o dir.o readdir.o \
-		copy_up.o export.o params.o
+		copy_up.o export.o params.o xattrs.o

fs/overlayfs/inode.c

···
 	return p;
 }
 
-bool ovl_is_private_xattr(struct super_block *sb, const char *name)
-{
-	struct ovl_fs *ofs = OVL_FS(sb);
-
-	if (ofs->config.userxattr)
-		return strncmp(name, OVL_XATTR_USER_PREFIX,
-			       sizeof(OVL_XATTR_USER_PREFIX) - 1) == 0;
-	else
-		return strncmp(name, OVL_XATTR_TRUSTED_PREFIX,
-			       sizeof(OVL_XATTR_TRUSTED_PREFIX) - 1) == 0;
-}
-
-int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
-		  const void *value, size_t size, int flags)
-{
-	int err;
-	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
-	struct dentry *upperdentry = ovl_i_dentry_upper(inode);
-	struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
-	struct path realpath;
-	const struct cred *old_cred;
-
-	if (!value && !upperdentry) {
-		ovl_path_lower(dentry, &realpath);
-		old_cred = ovl_override_creds(dentry->d_sb);
-		err = vfs_getxattr(mnt_idmap(realpath.mnt), realdentry, name, NULL, 0);
-		revert_creds(old_cred);
-		if (err < 0)
-			goto out;
-	}
-
-	if (!upperdentry) {
-		err = ovl_copy_up(dentry);
-		if (err)
-			goto out;
-
-		realdentry = ovl_dentry_upper(dentry);
-	}
-
-	err = ovl_want_write(dentry);
-	if (err)
-		goto out;
-
-	old_cred = ovl_override_creds(dentry->d_sb);
-	if (value) {
-		err = ovl_do_setxattr(ofs, realdentry, name, value, size,
-				      flags);
-	} else {
-		WARN_ON(flags != XATTR_REPLACE);
-		err = ovl_do_removexattr(ofs, realdentry, name);
-	}
-	revert_creds(old_cred);
-	ovl_drop_write(dentry);
-
-	/* copy c/mtime */
-	ovl_copyattr(inode);
-out:
-	return err;
-}
-
-int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
-		  void *value, size_t size)
-{
-	ssize_t res;
-	const struct cred *old_cred;
-	struct path realpath;
-
-	ovl_i_path_real(inode, &realpath);
-	old_cred = ovl_override_creds(dentry->d_sb);
-	res = vfs_getxattr(mnt_idmap(realpath.mnt), realpath.dentry, name, value, size);
-	revert_creds(old_cred);
-	return res;
-}
-
-static bool ovl_can_list(struct super_block *sb, const char *s)
-{
-	/* Never list private (.overlay) */
-	if (ovl_is_private_xattr(sb, s))
-		return false;
-
-	/* List all non-trusted xattrs */
-	if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
-		return true;
-
-	/* list other trusted for superuser only */
-	return ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
-}
-
-ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
-{
-	struct dentry *realdentry = ovl_dentry_real(dentry);
-	ssize_t res;
-	size_t len;
-	char *s;
-	const struct cred *old_cred;
-
-	old_cred = ovl_override_creds(dentry->d_sb);
-	res = vfs_listxattr(realdentry, list, size);
-	revert_creds(old_cred);
-	if (res <= 0 || size == 0)
-		return res;
-
-	/* filter out private xattrs */
-	for (s = list, len = res; len;) {
-		size_t slen = strnlen(s, len) + 1;
-
-		/* underlying fs providing us with an broken xattr list? */
-		if (WARN_ON(slen > len))
-			return -EIO;
-
-		len -= slen;
-		if (!ovl_can_list(dentry->d_sb, s)) {
-			res -= slen;
-			memmove(s, s + slen, len);
-		} else {
-			s += slen;
-		}
-	}
-
-	return res;
-}
-
 #ifdef CONFIG_FS_POSIX_ACL
 /*
  * Apply the idmapping of the layer to POSIX ACLs. The caller must pass a clone

fs/overlayfs/overlayfs.h

···
 unsigned int ovl_get_nlink(struct ovl_fs *ofs, struct dentry *lowerdentry,
 			   struct dentry *upperdentry,
 			   unsigned int fallback);
-int ovl_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
-		struct iattr *attr);
-int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
-		struct kstat *stat, u32 request_mask, unsigned int flags);
 int ovl_permission(struct mnt_idmap *idmap, struct inode *inode,
 		   int mask);
-int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
-		  const void *value, size_t size, int flags);
-int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
-		  void *value, size_t size);
-ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);
 
 #ifdef CONFIG_FS_POSIX_ACL
 struct posix_acl *do_ovl_get_acl(struct mnt_idmap *idmap,
···
 {
 	return (!ovl_upper_mnt(ofs) || !ofs->workdir);
 }
+
+/* xattr.c */
+
+const struct xattr_handler * const *ovl_xattr_handlers(struct ovl_fs *ofs);
+int ovl_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		struct iattr *attr);
+int ovl_getattr(struct mnt_idmap *idmap, const struct path *path,
+		struct kstat *stat, u32 request_mask, unsigned int flags);
+ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size);

fs/overlayfs/super.c

···
 	return ok;
 }
 
-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)
-{
-	return -EOPNOTSUPP;
-}
-
-static int ovl_own_xattr_set(const struct xattr_handler *handler,
-			     struct mnt_idmap *idmap,
-			     struct dentry *dentry, struct inode *inode,
-			     const char *name, const void *value,
-			     size_t size, int flags)
-{
-	return -EOPNOTSUPP;
-}
-
-static int ovl_other_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, name, buffer, size);
-}
-
-static int ovl_other_xattr_set(const struct xattr_handler *handler,
-			       struct mnt_idmap *idmap,
-			       struct dentry *dentry, struct inode *inode,
-			       const char *name, const void *value,
-			       size_t size, int flags)
-{
-	return ovl_xattr_set(dentry, inode, name, value, size, flags);
-}
-
-static const struct xattr_handler ovl_own_trusted_xattr_handler = {
-	.prefix	= OVL_XATTR_TRUSTED_PREFIX,
-	.get = ovl_own_xattr_get,
-	.set = ovl_own_xattr_set,
-};
-
-static const struct xattr_handler ovl_own_user_xattr_handler = {
-	.prefix	= OVL_XATTR_USER_PREFIX,
-	.get = ovl_own_xattr_get,
-	.set = ovl_own_xattr_set,
-};
-
-static const struct xattr_handler ovl_other_xattr_handler = {
-	.prefix	= "", /* catch all */
-	.get = ovl_other_xattr_get,
-	.set = ovl_other_xattr_set,
-};
-
-static const struct xattr_handler * const ovl_trusted_xattr_handlers[] = {
-	&ovl_own_trusted_xattr_handler,
-	&ovl_other_xattr_handler,
-	NULL
-};
-
-static const struct xattr_handler * const ovl_user_xattr_handlers[] = {
-	&ovl_own_user_xattr_handler,
-	&ovl_other_xattr_handler,
-	NULL
-};
-
 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
 			  struct inode **ptrap, const char *name)
 {
···
 	cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
 
 	sb->s_magic = OVERLAYFS_SUPER_MAGIC;
-	sb->s_xattr = ofs->config.userxattr ? ovl_user_xattr_handlers :
-		ovl_trusted_xattr_handlers;
+	sb->s_xattr = ovl_xattr_handlers(ofs);
 	sb->s_fs_info = ofs;
 #ifdef CONFIG_FS_POSIX_ACL
 	sb->s_flags |= SB_POSIXACL;

fs/overlayfs/xattrs.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/fs.h>
+#include <linux/xattr.h>
+#include "overlayfs.h"
+
+bool ovl_is_private_xattr(struct super_block *sb, const char *name)
+{
+	struct ovl_fs *ofs = OVL_FS(sb);
+
+	if (ofs->config.userxattr)
+		return strncmp(name, OVL_XATTR_USER_PREFIX,
+			       sizeof(OVL_XATTR_USER_PREFIX) - 1) == 0;
+	else
+		return strncmp(name, OVL_XATTR_TRUSTED_PREFIX,
+			       sizeof(OVL_XATTR_TRUSTED_PREFIX) - 1) == 0;
+}
+
+static int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
+			 const void *value, size_t size, int flags)
+{
+	int err;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+	struct dentry *upperdentry = ovl_i_dentry_upper(inode);
+	struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
+	struct path realpath;
+	const struct cred *old_cred;
+
+	if (!value && !upperdentry) {
+		ovl_path_lower(dentry, &realpath);
+		old_cred = ovl_override_creds(dentry->d_sb);
+		err = vfs_getxattr(mnt_idmap(realpath.mnt), realdentry, name, NULL, 0);
+		revert_creds(old_cred);
+		if (err < 0)
+			goto out;
+	}
+
+	if (!upperdentry) {
+		err = ovl_copy_up(dentry);
+		if (err)
+			goto out;
+
+		realdentry = ovl_dentry_upper(dentry);
+	}
+
+	err = ovl_want_write(dentry);
+	if (err)
+		goto out;
+
+	old_cred = ovl_override_creds(dentry->d_sb);
+	if (value) {
+		err = ovl_do_setxattr(ofs, realdentry, name, value, size,
+				      flags);
+	} else {
+		WARN_ON(flags != XATTR_REPLACE);
+		err = ovl_do_removexattr(ofs, realdentry, name);
+	}
+	revert_creds(old_cred);
+	ovl_drop_write(dentry);
+
+	/* copy c/mtime */
+	ovl_copyattr(inode);
+out:
+	return err;
+}
+
+static int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
+			 void *value, size_t size)
+{
+	ssize_t res;
+	const struct cred *old_cred;
+	struct path realpath;
+
+	ovl_i_path_real(inode, &realpath);
+	old_cred = ovl_override_creds(dentry->d_sb);
+	res = vfs_getxattr(mnt_idmap(realpath.mnt), realpath.dentry, name, value, size);
+	revert_creds(old_cred);
+	return res;
+}
+
+static bool ovl_can_list(struct super_block *sb, const char *s)
+{
+	/* Never list private (.overlay) */
+	if (ovl_is_private_xattr(sb, s))
+		return false;
+
+	/* List all non-trusted xattrs */
+	if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
+		return true;
+
+	/* list other trusted for superuser only */
+	return ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
+}
+
+ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
+{
+	struct dentry *realdentry = ovl_dentry_real(dentry);
+	ssize_t res;
+	size_t len;
+	char *s;
+	const struct cred *old_cred;
+
+	old_cred = ovl_override_creds(dentry->d_sb);
+	res = vfs_listxattr(realdentry, list, size);
+	revert_creds(old_cred);
+	if (res <= 0 || size == 0)
+		return res;
+
+	/* filter out private xattrs */
+	for (s = list, len = res; len;) {
+		size_t slen = strnlen(s, len) + 1;
+
+		/* underlying fs providing us with an broken xattr list? */
+		if (WARN_ON(slen > len))
+			return -EIO;
+
+		len -= slen;
+		if (!ovl_can_list(dentry->d_sb, s)) {
+			res -= slen;
+			memmove(s, s + slen, len);
+		} else {
+			s += slen;
+		}
+	}
+
+	return res;
+}
+
+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)
+{
+	return -EOPNOTSUPP;
+}
+
+static int ovl_own_xattr_set(const struct xattr_handler *handler,
+			     struct mnt_idmap *idmap,
+			     struct dentry *dentry, struct inode *inode,
+			     const char *name, const void *value,
+			     size_t size, int flags)
+{
+	return -EOPNOTSUPP;
+}
+
+static int ovl_other_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, name, buffer, size);
+}
+
+static int ovl_other_xattr_set(const struct xattr_handler *handler,
+			       struct mnt_idmap *idmap,
+			       struct dentry *dentry, struct inode *inode,
+			       const char *name, const void *value,
+			       size_t size, int flags)
+{
+	return ovl_xattr_set(dentry, inode, name, value, size, flags);
+}
+
+static const struct xattr_handler ovl_own_trusted_xattr_handler = {
+	.prefix	= OVL_XATTR_TRUSTED_PREFIX,
+	.get = ovl_own_xattr_get,
+	.set = ovl_own_xattr_set,
+};
+
+static const struct xattr_handler ovl_own_user_xattr_handler = {
+	.prefix	= OVL_XATTR_USER_PREFIX,
+	.get = ovl_own_xattr_get,
+	.set = ovl_own_xattr_set,
+};
+
+static const struct xattr_handler ovl_other_xattr_handler = {
+	.prefix	= "", /* catch all */
+	.get = ovl_other_xattr_get,
+	.set = ovl_other_xattr_set,
+};
+
+static const struct xattr_handler * const ovl_trusted_xattr_handlers[] = {
+	&ovl_own_trusted_xattr_handler,
+	&ovl_other_xattr_handler,
+	NULL
+};
+
+static const struct xattr_handler * const ovl_user_xattr_handlers[] = {
+	&ovl_own_user_xattr_handler,
+	&ovl_other_xattr_handler,
+	NULL
+};
+
+const struct xattr_handler * const *ovl_xattr_handlers(struct ovl_fs *ofs)
+{
+	return ofs->config.userxattr ? ovl_user_xattr_handlers :
+		ovl_trusted_xattr_handlers;
+}
+