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Subject[PATCH -V3 09/17] richacl: Helper functions for implementing richacl inode operations
Date
From: Andreas Gruenbacher <agruen@suse.de>

These functions are supposed to be used by file systems so that the file
system independent code remains in the vfs.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/Makefile | 2 +-
fs/richacl_inode.c | 195 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/richacl.h | 21 +++++
3 files changed, 217 insertions(+), 1 deletions(-)
create mode 100644 fs/richacl_inode.c
diff --git a/fs/Makefile b/fs/Makefile
index 9ecd045..b38cfc7 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -52,7 +52,7 @@ obj-$(CONFIG_NFS_COMMON) += nfs_common/
obj-$(CONFIG_GENERIC_ACL) += generic_acl.o

obj-$(CONFIG_FS_RICHACL) += richacl.o
-richacl-y := richacl_base.o
+richacl-y := richacl_base.o richacl_inode.o

obj-y += quota/

diff --git a/fs/richacl_inode.c b/fs/richacl_inode.c
new file mode 100644
index 0000000..9e80b33
--- /dev/null
+++ b/fs/richacl_inode.c
@@ -0,0 +1,195 @@
+/*
+ * Copyright (C) 2010 Novell, Inc.
+ * Written by Andreas Gruenbacher <agruen@suse.de>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * 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/sched.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/richacl.h>
+
+/**
+ * richacl_may_create - helper for implementing iop->may_create
+ */
+int
+richacl_may_create(struct inode *dir, int isdir,
+ int (*richacl_permission)(struct inode *, unsigned int))
+{
+ if (IS_RICHACL(dir))
+ return richacl_permission(dir,
+ ACE4_EXECUTE | (isdir ?
+ ACE4_ADD_SUBDIRECTORY : ACE4_ADD_FILE));
+ else
+ return generic_permission(dir, MAY_WRITE | MAY_EXEC,
+ dir->i_op->check_acl);
+}
+EXPORT_SYMBOL(richacl_may_create);
+
+static int
+check_sticky(struct inode *dir, struct inode *inode)
+{
+ if (!(dir->i_mode & S_ISVTX))
+ return 0;
+ if (inode->i_uid == current_fsuid())
+ return 0;
+ if (dir->i_uid == current_fsuid())
+ return 0;
+ return !capable(CAP_FOWNER);
+}
+
+/**
+ * richacl_may_delete - helper for implementing iop->may_delete
+ */
+int
+richacl_may_delete(struct inode *dir, struct inode *inode, int replace,
+ int (*richacl_permission)(struct inode *, unsigned int))
+{
+ int error;
+
+ if (IS_RICHACL(inode)) {
+ unsigned int mask = ACE4_EXECUTE | ACE4_DELETE_CHILD;
+ if (replace)
+ mask |= S_ISDIR(inode->i_mode) ?
+ ACE4_ADD_SUBDIRECTORY : ACE4_ADD_FILE;
+ error = richacl_permission(dir, mask);
+ if (error &&
+ !richacl_permission(dir, ACE4_EXECUTE) &&
+ !richacl_permission(inode, ACE4_DELETE))
+ error = 0;
+ else if (!error && check_sticky(dir, inode))
+ error = -EPERM;
+ } else {
+ error = generic_permission(dir, MAY_WRITE | MAY_EXEC,
+ dir->i_op->check_acl);
+ if (!error && check_sticky(dir, inode))
+ error = -EPERM;
+ }
+
+ return error;
+}
+EXPORT_SYMBOL(richacl_may_delete);
+
+/**
+ * richacl_inode_permission - helper for implementing iop->permission
+ * @inode: inode to check
+ * @acl: rich acl of the inode (may be NULL)
+ * @mask: requested access (ACE4_* bitmask)
+ *
+ * This function is supposed to be used by file systems for implementing the
+ * permission inode operation.
+ */
+int
+richacl_inode_permission(struct inode *inode, const struct richacl *acl,
+ unsigned int mask)
+{
+ if (acl) {
+ if (!richacl_permission(inode, acl, mask))
+ return 0;
+ } else {
+ int mode = inode->i_mode;
+
+ if (current_fsuid() == inode->i_uid)
+ mode >>= 6;
+ else if (in_group_p(inode->i_gid))
+ mode >>= 3;
+ if (!(mask & ~richacl_mode_to_mask(mode)))
+ return 0;
+ }
+
+ /*
+ * Keep in sync with the capability checks in generic_permission().
+ */
+ if (!(mask & ~ACE4_POSIX_MODE_ALL)) {
+ /*
+ * Read/write DACs are always overridable.
+ * Executable DACs are overridable if at
+ * least one exec bit is set.
+ */
+ if (!(mask & ACE4_POSIX_MODE_EXEC) || execute_ok(inode))
+ if (capable(CAP_DAC_OVERRIDE))
+ return 0;
+ }
+ /*
+ * Searching includes executable on directories, else just read.
+ */
+ if (!(mask & ~(ACE4_READ_DATA | ACE4_LIST_DIRECTORY | ACE4_EXECUTE)) &&
+ (S_ISDIR(inode->i_mode) || !(mask & ACE4_EXECUTE)))
+ if (capable(CAP_DAC_READ_SEARCH))
+ return 0;
+
+ return -EACCES;
+}
+EXPORT_SYMBOL_GPL(richacl_inode_permission);
+
+/**
+ * richacl_inode_change_ok - helper for implementing iop->setattr
+ * @inode: inode to check
+ * @attr: requested inode attribute changes
+ * @richacl_permission: permission function taking an inode and ACE4_* flags
+ *
+ * Keep in sync with inode_change_ok().
+ */
+int
+richacl_inode_change_ok(struct inode *inode, struct iattr *attr,
+ int (*richacl_permission)(struct inode *, unsigned int))
+{
+ unsigned int ia_valid = attr->ia_valid;
+
+ /* If force is set do it anyway. */
+ if (ia_valid & ATTR_FORCE)
+ return 0;
+
+ /* Make sure a caller can chown. */
+ if ((ia_valid & ATTR_UID) &&
+ (current_fsuid() != inode->i_uid ||
+ attr->ia_uid != inode->i_uid) &&
+ (current_fsuid() != attr->ia_uid ||
+ richacl_permission(inode, ACE4_WRITE_OWNER)) &&
+ !capable(CAP_CHOWN))
+ goto error;
+
+ /* Make sure caller can chgrp. */
+ if ((ia_valid & ATTR_GID)) {
+ int in_group = in_group_p(attr->ia_gid);
+ if ((current_fsuid() != inode->i_uid ||
+ (!in_group && attr->ia_gid != inode->i_gid)) &&
+ (!in_group ||
+ richacl_permission(inode, ACE4_WRITE_OWNER)) &&
+ !capable(CAP_CHOWN))
+ goto error;
+ }
+
+ /* Make sure a caller can chmod. */
+ if (ia_valid & ATTR_MODE) {
+ if (current_fsuid() != inode->i_uid &&
+ richacl_permission(inode, ACE4_WRITE_ACL) &&
+ !capable(CAP_FOWNER))
+ goto error;
+ /* Also check the setgid bit! */
+ if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
+ inode->i_gid) && !capable(CAP_FSETID))
+ attr->ia_mode &= ~S_ISGID;
+ }
+
+ /* Check for setting the inode time. */
+ if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET)) {
+ if (current_fsuid() != inode->i_uid &&
+ richacl_permission(inode, ACE4_WRITE_ATTRIBUTES) &&
+ !capable(CAP_FOWNER))
+ goto error;
+ }
+ return 0;
+error:
+ return -EPERM;
+}
+EXPORT_SYMBOL_GPL(richacl_inode_change_ok);
diff --git a/include/linux/richacl.h b/include/linux/richacl.h
index c9d2761..f6f892d 100644
--- a/include/linux/richacl.h
+++ b/include/linux/richacl.h
@@ -292,4 +292,25 @@ extern struct richacl *richacl_chmod(struct richacl *, mode_t);
extern int richacl_permission(struct inode *, const struct richacl *,
unsigned int);

+/* richacl_inode.c */
+
+#ifdef CONFIG_FS_RICHACL
+extern int richacl_may_create(struct inode *, int,
+ int (*)(struct inode *, unsigned int));
+extern int richacl_may_delete(struct inode *, struct inode *, int,
+ int (*)(struct inode *, unsigned int));
+extern int richacl_inode_permission(struct inode *, const struct richacl *,
+ unsigned int);
+extern int richacl_inode_change_ok(struct inode *, struct iattr *,
+ int (*)(struct inode *, unsigned int));
+#else
+static inline int
+richacl_inode_change_ok(struct inode *inode, struct iattr *attr,
+ int (*richacl_permission)(struct inode *inode,
+ unsigned int mask))
+{
+ return -EPERM;
+}
+#endif
+
#endif /* __RICHACL_H */
--
1.7.0.4


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