Add POSIX ACL support

Add support for the POSIX ACLs as described in acl(5).  Support is
enabled by default and can be explicitly enabled or disabled with the
acl or noacl mount options, respectively.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/src/Makefile

@@ -8,6 +8,7 @@ CFLAGS_scoutfs_trace.o = -I$(src) # define_trace.h double include
 -include $(src)/Makefile.kernelcompat
  
 scoutfs-y +=			\
+	acl.o			\
 	avl.o			\
 	alloc.o			\
 	block.o			\

kmod/src/acl.c

@@ -0,0 +1,355 @@
+/*
+ * Copyright (C) 2022 Versity Software, Inc.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/xattr.h>
+#include <linux/posix_acl.h>
+#include <linux/posix_acl_xattr.h>
+
+#include "format.h"
+#include "super.h"
+#include "scoutfs_trace.h"
+#include "xattr.h"
+#include "acl.h"
+#include "inode.h"
+#include "trans.h"
+
+/*
+ * POSIX draft ACLs are stored as full xattr items with the entries
+ * encoded as the kernel's posix_acl_xattr_{header,entry} value structs.
+ *
+ * They're accessed and modified via user facing synthetic xattrs, iops
+ * calls from the kernel, during inode mode changes, and during inode
+ * creation.
+ *
+ * ACL access devolves into xattr access which is relatively expensive
+ * so we maintain the cached native form in the vfs inode.  We drop the
+ * cache in lock invalidation which means that cached acl access must
+ * always be performed under cluster locking.
+ */
+
+static int acl_xattr_name_len(int type, char **name, size_t *name_len)
+{
+	int ret = 0;
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		*name = XATTR_NAME_POSIX_ACL_ACCESS;
+		if (name_len)
+			*name_len = sizeof(XATTR_NAME_POSIX_ACL_ACCESS) - 1;
+		break;
+	case ACL_TYPE_DEFAULT:
+		*name = XATTR_NAME_POSIX_ACL_DEFAULT;
+		if (name_len)
+			*name_len = sizeof(XATTR_NAME_POSIX_ACL_DEFAULT) - 1;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+struct posix_acl *scoutfs_get_acl_locked(struct inode *inode, int type, struct scoutfs_lock *lock)
+{
+	struct posix_acl *acl;
+	char *value = NULL;
+	char *name;
+	int ret;
+
+	if (!IS_POSIXACL(inode))
+		return NULL;
+
+	acl = get_cached_acl(inode, type);
+	if (acl != ACL_NOT_CACHED)
+		return acl;
+
+	ret = acl_xattr_name_len(type, &name, NULL);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	ret = scoutfs_xattr_get_locked(inode, name, NULL, 0, lock);
+	if (ret > 0) {
+		value = kzalloc(ret, GFP_NOFS);
+		if (!value)
+			ret = -ENOMEM;
+		else
+			ret = scoutfs_xattr_get_locked(inode, name, value, ret, lock);
+	}
+	if (ret > 0) {
+		acl = posix_acl_from_xattr(&init_user_ns, value, ret);
+	} else if (ret == -ENODATA || ret == 0) {
+		acl = NULL;
+	} else {
+		acl = ERR_PTR(ret);
+	}
+
+	/* can set null negative cache */
+	if (!IS_ERR(acl))
+		set_cached_acl(inode, type, acl);
+
+	kfree(value);
+
+	return acl;
+}
+
+struct posix_acl *scoutfs_get_acl(struct inode *inode, int type)
+{
+	struct super_block *sb = inode->i_sb;
+	struct scoutfs_lock *lock = NULL;
+	struct posix_acl *acl;
+	int ret;
+
+	if (!IS_POSIXACL(inode))
+		return NULL;
+
+	ret = scoutfs_lock_inode(sb, SCOUTFS_LOCK_READ, 0, inode, &lock);
+	if (ret < 0) {
+		acl = ERR_PTR(ret);
+	} else {
+		acl = scoutfs_get_acl_locked(inode, type, lock);
+		scoutfs_unlock(sb, lock, SCOUTFS_LOCK_READ);
+	}
+
+	return acl;
+}
+
+/*
+ * The caller has acquired the locks and dirtied the inode, they'll
+ * update the inode item if we return 0.
+ */
+int scoutfs_set_acl_locked(struct inode *inode, struct posix_acl *acl, int type,
+			   struct scoutfs_lock *lock, struct list_head *ind_locks)
+{
+	static const struct scoutfs_xattr_prefix_tags tgs = {0,}; /* never scoutfs. prefix */
+	bool set_mode = false;
+	char *value = NULL;
+	umode_t new_mode;
+	size_t name_len;
+	char *name;
+	int size = 0;
+	int ret;
+
+	ret = acl_xattr_name_len(type, &name, &name_len);
+	if (ret < 0)
+		return ret;
+
+	switch (type) {
+	case ACL_TYPE_ACCESS:
+		if (acl) {
+			ret = posix_acl_update_mode(inode, &new_mode, &acl);
+			if (ret < 0)
+				goto out;
+			set_mode = true;
+		}
+		break;
+	case ACL_TYPE_DEFAULT:
+		if (!S_ISDIR(inode->i_mode)) {
+			ret = acl ? -EINVAL : 0;
+			goto out;
+		}
+		break;
+	}
+
+	if (acl) {
+		size = posix_acl_xattr_size(acl->a_count);
+		value = kmalloc(size, GFP_NOFS);
+		if (!value) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		ret = posix_acl_to_xattr(&init_user_ns, acl, value, size);
+		if (ret < 0)
+			goto out;
+	}
+
+	ret = scoutfs_xattr_set_locked(inode, name, name_len, value, size, 0, &tgs,
+				       lock, NULL, ind_locks);
+	if (ret == 0 && set_mode) {
+		inode->i_mode = new_mode;
+		if (!value) {
+			/* can be setting an acl that only affects mode, didn't need xattr */
+			inode_inc_iversion(inode);
+			inode->i_ctime = CURRENT_TIME;
+		}
+	}
+
+out:
+	if (!ret)
+		set_cached_acl(inode, type, acl);
+
+	kfree(value);
+
+	return ret;
+}
+
+int scoutfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
+{
+	struct super_block *sb = inode->i_sb;
+	struct scoutfs_lock *lock = NULL;
+	LIST_HEAD(ind_locks);
+	int ret;
+
+	ret = scoutfs_lock_inode(sb, SCOUTFS_LOCK_WRITE, SCOUTFS_LKF_REFRESH_INODE, inode, &lock) ?:
+	      scoutfs_inode_index_lock_hold(inode, &ind_locks, false, true);
+	if (ret == 0) {
+		ret = scoutfs_dirty_inode_item(inode, lock) ?:
+		      scoutfs_set_acl_locked(inode, acl, type, lock, &ind_locks);
+		if (ret == 0)
+			scoutfs_update_inode_item(inode, lock, &ind_locks);
+
+		scoutfs_release_trans(sb);
+		scoutfs_inode_index_unlock(sb, &ind_locks);
+	}
+
+	scoutfs_unlock(sb, lock, SCOUTFS_LOCK_WRITE);
+	return ret;
+}
+
+int scoutfs_acl_get_xattr(struct dentry *dentry, const char *name, void *value, size_t size,
+			  int type)
+{
+	struct posix_acl *acl;
+	int ret = 0;
+
+	if (!IS_POSIXACL(dentry->d_inode))
+		return -EOPNOTSUPP;
+
+	acl = scoutfs_get_acl(dentry->d_inode, type);
+	if (IS_ERR(acl))
+		return PTR_ERR(acl);
+	if (acl == NULL)
+		return -ENODATA;
+
+	ret = posix_acl_to_xattr(&init_user_ns, acl, value, size);
+	posix_acl_release(acl);
+
+	return ret;
+}
+
+int scoutfs_acl_set_xattr(struct dentry *dentry, const char *name, const void *value, size_t size,
+			  int flags, int type)
+{
+	struct posix_acl *acl = NULL;
+	int ret;
+
+	if (!inode_owner_or_capable(dentry->d_inode))
+		return -EPERM;
+
+	if (!IS_POSIXACL(dentry->d_inode))
+		return -EOPNOTSUPP;
+
+	if (value) {
+		acl = posix_acl_from_xattr(&init_user_ns, value, size);
+		if (IS_ERR(acl))
+			return PTR_ERR(acl);
+
+		if (acl) {
+			ret = posix_acl_valid(&init_user_ns, acl);
+			if (ret)
+				goto out;
+		}
+	}
+
+	ret = scoutfs_set_acl(dentry->d_inode, acl, type);
+out:
+	posix_acl_release(acl);
+
+	return ret;
+}
+
+/*
+ * Apply the parent's default acl to new inodes access acl and inherit
+ * it as the default for new directories.  The caller holds locks and a
+ * transaction.
+ */
+int scoutfs_init_acl_locked(struct inode *inode, struct inode *dir,
+			    struct scoutfs_lock *lock, struct scoutfs_lock *dir_lock,
+			    struct list_head *ind_locks)
+{
+	struct posix_acl *acl = NULL;
+	int ret = 0;
+
+	if (!S_ISLNK(inode->i_mode)) {
+		if (IS_POSIXACL(dir)) {
+			acl = scoutfs_get_acl_locked(dir, ACL_TYPE_DEFAULT, dir_lock);
+			if (IS_ERR(acl))
+				return PTR_ERR(acl);
+		}
+
+		if (!acl)
+			inode->i_mode &= ~current_umask();
+	}
+
+	if (IS_POSIXACL(dir) && acl) {
+		if (S_ISDIR(inode->i_mode)) {
+			ret = scoutfs_set_acl_locked(inode, acl, ACL_TYPE_DEFAULT,
+						     lock, ind_locks);
+			if (ret)
+				goto out;
+		}
+		ret = posix_acl_create(&acl, GFP_NOFS, &inode->i_mode);
+		if (ret < 0)
+			return ret;
+		if (ret > 0)
+			ret = scoutfs_set_acl_locked(inode, acl, ACL_TYPE_ACCESS,
+						     lock, ind_locks);
+	} else {
+		cache_no_acl(inode);
+	}
+out:
+	posix_acl_release(acl);
+	return ret;
+}
+
+/*
+ * Update the access ACL based on a newly set mode.  If we return an
+ * error then the xattr wasn't changed.
+ *
+ * Annoyingly, setattr_copy has logic that transforms the final set mode
+ * that we want to use to update the acl.   But we don't want to modify
+ * the other inode fields while discovering the resulting mode.  We're
+ * relying on acl_chmod not caring about the transformation (currently
+ * just clears sgid).  It would be better if we could get the resulting
+ * mode to give to acl_chmod without modifying the other inode fields.
+ *
+ * The caller has the inode mutex, a cluster lock, transaction, and will
+ * update the inode item if we return success.
+ */
+int scoutfs_acl_chmod_locked(struct inode *inode, struct iattr *attr,
+			     struct scoutfs_lock *lock, struct list_head *ind_locks)
+{
+	struct posix_acl *acl;
+	int ret = 0;
+
+	if (!IS_POSIXACL(inode) || !(attr->ia_valid & ATTR_MODE))
+		return 0;
+
+	if (S_ISLNK(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	acl = scoutfs_get_acl_locked(inode, ACL_TYPE_ACCESS, lock);
+	if (IS_ERR_OR_NULL(acl))
+		return PTR_ERR(acl);
+
+	ret = posix_acl_chmod(&acl, GFP_KERNEL, attr->ia_mode);
+	if (ret)
+		return ret;
+
+	ret = scoutfs_set_acl_locked(inode, acl, ACL_TYPE_ACCESS, lock, ind_locks);
+	posix_acl_release(acl);
+	return ret;
+}

kmod/src/acl.h

@@ -0,0 +1,18 @@
+#ifndef _SCOUTFS_ACL_H_
+#define _SCOUTFS_ACL_H_
+
+struct posix_acl *scoutfs_get_acl(struct inode *inode, int type);
+struct posix_acl *scoutfs_get_acl_locked(struct inode *inode, int type, struct scoutfs_lock *lock);
+int scoutfs_set_acl(struct inode *inode, struct posix_acl *acl, int type);
+int scoutfs_set_acl_locked(struct inode *inode, struct posix_acl *acl, int type,
+			   struct scoutfs_lock *lock, struct list_head *ind_locks);
+int scoutfs_acl_get_xattr(struct dentry *dentry, const char *name, void *value, size_t size,
+			  int type);
+int scoutfs_acl_set_xattr(struct dentry *dentry, const char *name, const void *value, size_t size,
+			  int flags, int type);
+int scoutfs_acl_chmod_locked(struct inode *inode, struct iattr *attr,
+			     struct scoutfs_lock *lock, struct list_head *ind_locks);
+int scoutfs_init_acl_locked(struct inode *inode, struct inode *dir,
+			    struct scoutfs_lock *lock, struct scoutfs_lock *dir_lock,
+			    struct list_head *ind_locks);
+#endif

kmod/src/dir.c

@@ -32,6 +32,7 @@
 #include "hash.h"
 #include "omap.h"
 #include "forest.h"
+#include "acl.h"
 #include "counters.h"
 #include "scoutfs_trace.h"
 
@@ -765,7 +766,8 @@ retry:
 	if (ret)
 		goto out_unlock;
 
-	ret = scoutfs_new_inode(sb, dir, mode, rdev, ino, *inode_lock, &inode);
+	ret = scoutfs_new_inode(sb, dir, mode, rdev, ino, *inode_lock, &inode) ?:
+	      scoutfs_init_acl_locked(inode, dir, *inode_lock, *dir_lock, ind_locks);
 	if (ret < 0)
 		goto out;
 
@@ -1246,6 +1248,7 @@ const struct inode_operations scoutfs_symlink_iops = {
 	.getxattr	= generic_getxattr,
 	.listxattr	= scoutfs_listxattr,
 	.removexattr	= generic_removexattr,
+	.get_acl	= scoutfs_get_acl,
 };
 
 /*
@@ -1982,6 +1985,7 @@ const struct inode_operations_wrapper scoutfs_dir_iops = {
 	.getxattr	= generic_getxattr,
 	.listxattr	= scoutfs_listxattr,
 	.removexattr	= generic_removexattr,
+	.get_acl	= scoutfs_get_acl,
 	.symlink	= scoutfs_symlink,
 	.permission	= scoutfs_permission,
 	},

kmod/src/inode.c

@@ -36,6 +36,7 @@
 #include "omap.h"
 #include "forest.h"
 #include "btree.h"
+#include "acl.h"
 
 /*
  * XXX
@@ -140,6 +141,7 @@ static const struct inode_operations scoutfs_file_iops = {
 	.getxattr	= generic_getxattr,
 	.listxattr	= scoutfs_listxattr,
 	.removexattr	= generic_removexattr,
+	.get_acl	= scoutfs_get_acl,
 	.fiemap		= scoutfs_data_fiemap,
 };
 
@@ -150,6 +152,7 @@ static const struct inode_operations scoutfs_special_iops = {
 	.getxattr	= generic_getxattr,
 	.listxattr	= scoutfs_listxattr,
 	.removexattr	= generic_removexattr,
+	.get_acl	= scoutfs_get_acl,
 };
 
 /*
@@ -507,10 +510,15 @@ retry:
 	if (ret)
 		goto out;
 
+	ret = scoutfs_acl_chmod_locked(inode, attr, lock, &ind_locks);
+	if (ret < 0)
+		goto release;
+
 	setattr_copy(inode, attr);
 	inode_inc_iversion(inode);
 	scoutfs_update_inode_item(inode, lock, &ind_locks);
 
+release:
 	scoutfs_release_trans(sb);
 	scoutfs_inode_index_unlock(sb, &ind_locks);
 out:

kmod/src/lock.c

@@ -18,6 +18,7 @@
 #include <linux/mm.h>
 #include <linux/sort.h>
 #include <linux/ctype.h>
+#include <linux/posix_acl.h>
 
 #include "super.h"
 #include "lock.h"
@@ -156,6 +157,8 @@ static void invalidate_inode(struct super_block *sb, u64 ino)
 		if (!linfo->unmounting)
 			d_prune_aliases(inode);
 
+		forget_all_cached_acls(inode);
+
 		si->drop_invalidated = true;
 		if (scoutfs_lock_is_covered(sb, &si->ino_lock_cov) && inode->i_nlink > 0) {
 			iput(inode);

kmod/src/options.c

@@ -29,14 +29,18 @@
 #include "inode.h"
 
 enum {
+	Opt_acl,
 	Opt_metadev_path,
+	Opt_noacl,
 	Opt_orphan_scan_delay_ms,
 	Opt_quorum_slot_nr,
 	Opt_err,
 };
 
 static const match_table_t tokens = {
+	{Opt_acl, "acl"},
 	{Opt_metadev_path, "metadev_path=%s"},
+	{Opt_noacl, "noacl"},
 	{Opt_orphan_scan_delay_ms, "orphan_scan_delay_ms=%s"},
 	{Opt_quorum_slot_nr, "quorum_slot_nr=%s"},
 	{Opt_err, NULL}
@@ -134,12 +138,20 @@ static int parse_options(struct super_block *sb, char *options, struct scoutfs_m
 		token = match_token(p, tokens, args);
 		switch (token) {
 
+		case Opt_acl:
+			sb->s_flags |= MS_POSIXACL;
+			break;
+
 		case Opt_metadev_path:
 			ret = parse_bdev_path(sb, &args[0], &opts->metadev_path);
 			if (ret < 0)
 				return ret;
 			break;
 
+		case Opt_noacl:
+			sb->s_flags &= ~MS_POSIXACL;
+			break;
+
 		case Opt_orphan_scan_delay_ms:
 			if (opts->orphan_scan_delay_ms != -1) {
 				scoutfs_err(sb, "multiple orphan_scan_delay_ms options provided, only provide one.");
@@ -250,10 +262,15 @@ int scoutfs_options_show(struct seq_file *seq, struct dentry *root)
 {
 	struct super_block *sb = root->d_sb;
 	struct scoutfs_mount_options opts;
+	const bool is_acl = !!(sb->s_flags & MS_POSIXACL);
 
 	scoutfs_options_read(sb, &opts);
 
+	if (is_acl)
+		seq_puts(seq, ",acl");
 	seq_printf(seq, ",metadev_path=%s", opts.metadev_path);
+	if (!is_acl)
+		seq_puts(seq, ",noacl");
 	seq_printf(seq, ",orphan_scan_delay_ms=%u", opts.orphan_scan_delay_ms);
 	if (opts.quorum_slot_nr >= 0)
 		seq_printf(seq, ",quorum_slot_nr=%d", opts.quorum_slot_nr);

kmod/src/super.c

@@ -485,7 +485,7 @@ static int scoutfs_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_op = &scoutfs_super_ops;
 	sb->s_export_op = &scoutfs_export_ops;
 	sb->s_xattr = scoutfs_xattr_handlers;
-	sb->s_flags |= MS_I_VERSION;
+	sb->s_flags |= MS_I_VERSION | MS_POSIXACL;
 
 	/* btree blocks use long lived bh->b_data refs */
 	mapping_set_gfp_mask(sb->s_bdev->bd_inode->i_mapping, GFP_NOFS);

kmod/src/xattr.c

@@ -15,6 +15,7 @@
 #include <linux/dcache.h>
 #include <linux/xattr.h>
 #include <linux/crc32c.h>
+#include <linux/posix_acl.h>
 
 #include "format.h"
 #include "inode.h"
@@ -26,6 +27,7 @@
 #include "xattr.h"
 #include "lock.h"
 #include "hash.h"
+#include "acl.h"
 #include "scoutfs_trace.h"
 
 /*
@@ -902,11 +904,27 @@ static const struct xattr_handler scoutfs_xattr_security_handler = {
 	.set = scoutfs_xattr_set_handler,
 };
 
+static const struct xattr_handler scoutfs_xattr_acl_access_handler = {
+	.prefix = XATTR_NAME_POSIX_ACL_ACCESS,
+	.flags  = ACL_TYPE_ACCESS,
+	.get    = scoutfs_acl_get_xattr,
+	.set    = scoutfs_acl_set_xattr,
+};
+
+static const struct xattr_handler scoutfs_xattr_acl_default_handler = {
+	.prefix = XATTR_NAME_POSIX_ACL_DEFAULT,
+	.flags  = ACL_TYPE_DEFAULT,
+	.get    = scoutfs_acl_get_xattr,
+	.set    = scoutfs_acl_set_xattr,
+};
+
 const struct xattr_handler *scoutfs_xattr_handlers[] = {
 	&scoutfs_xattr_user_handler,
 	&scoutfs_xattr_scoutfs_handler,
 	&scoutfs_xattr_trusted_handler,
 	&scoutfs_xattr_security_handler,
+	&scoutfs_xattr_acl_access_handler,
+	&scoutfs_xattr_acl_default_handler,
 	NULL
 };
 

utils/man/scoutfs.5

@@ -15,12 +15,27 @@ general mount options described in the
 .BR mount (8)
 manual page.
 .TP
+.B acl
+The acl mount option enables support for POSIX Access Control Lists
+as detailed in
+.BR acl (5) .
+Support for POSIX ACLs is the default.
+.TP
 .B metadev_path=<device>
 The metadev_path option specifies the path to the block device that
 contains the filesystem's metadata.
 .sp
 This option is required.
 .TP
+.B noacl
+The noacl mount option disables the default support for POSIX Access
+Control Lists.  Any existing system.posix_acl_default and
+system.posix_acl_access extended attributes remain in inodes.   They
+will appear in listings from
+.BR listxattr (5)
+but specific retrieval or reomval operations will fail.  They will be
+used for enforcement again if ACL support is later enabled.
+.TP
 .B orphan_scan_delay_ms=<number>
 This option sets the average expected delay, in milliseconds, between
 each mount's scan of the global orphaned inode list.  Jitter is added to