[PATCH] Access Control Lists for tmpfs

Add access control lists for tmpfs.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 332 insertions, 2 deletions

diff --git a/fs/Kconfig b/fs/Kconfig
index deb9eec9f6ee..4fd9efac29ab 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -881,6 +881,19 @@ config TMPFS
 
           See <file:Documentation/filesystems/tmpfs.txt> for details.
 
+config TMPFS_POSIX_ACL
+        bool "Tmpfs POSIX Access Control Lists"
+        depends on TMPFS
+        select GENERIC_ACL
+        help
+          POSIX Access Control Lists (ACLs) support permissions for users and
+          groups beyond the owner/group/world scheme.
+
+          To learn more about Access Control Lists, visit the POSIX ACLs for
+          Linux website <http://acl.bestbits.at/>.
+
+          If you don't know what Access Control Lists are, say N.
+
 config HUGETLBFS
         bool "HugeTLB file system support"
         depends X86 || IA64 || PPC64 || SPARC64 || SUPERH || BROKEN
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index c057f0b32318..f3c51899117f 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -19,6 +19,10 @@ struct shmem_inode_info {
         swp_entry_t             i_direct[SHMEM_NR_DIRECT]; /* first blocks */
         struct list_head        swaplist;       /* chain of maybes on swap */
         struct inode            vfs_inode;
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        struct posix_acl        *i_acl;
+        struct posix_acl        *i_default_acl;
+#endif
 };
 
 struct shmem_sb_info {
@@ -36,4 +40,24 @@ static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
         return container_of(inode, struct shmem_inode_info, vfs_inode);
 }
 
+#ifdef CONFIG_TMPFS_POSIX_ACL
+int shmem_permission(struct inode *, int, struct nameidata *);
+int shmem_acl_init(struct inode *, struct inode *);
+void shmem_acl_destroy_inode(struct inode *);
+
+extern struct xattr_handler shmem_xattr_acl_access_handler;
+extern struct xattr_handler shmem_xattr_acl_default_handler;
+
+extern struct generic_acl_operations shmem_acl_ops;
+
+#else
+static inline int shmem_acl_init(struct inode *inode, struct inode *dir)
+{
+        return 0;
+}
+static inline void shmem_acl_destroy_inode(struct inode *inode)
+{
+}
+#endif  /* CONFIG_TMPFS_POSIX_ACL */
+
 #endif
diff --git a/mm/Makefile b/mm/Makefile
index 60c56c0b5e10..6200c6d6afd2 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_HUGETLBFS)	+= hugetlb.o
 obj-$(CONFIG_NUMA)      += mempolicy.o
 obj-$(CONFIG_SPARSEMEM) += sparse.o
 obj-$(CONFIG_SHMEM) += shmem.o
+obj-$(CONFIG_TMPFS_POSIX_ACL) += shmem_acl.o
 obj-$(CONFIG_TINY_SHMEM) += tiny-shmem.o
 obj-$(CONFIG_SLOB) += slob.o
 obj-$(CONFIG_SLAB) += slab.o
diff --git a/mm/shmem.c b/mm/shmem.c
index eda907c3a86a..b96de69f236b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -26,6 +26,8 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/fs.h>
+#include <linux/xattr.h>
+#include <linux/generic_acl.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include <linux/file.h>
@@ -177,6 +179,7 @@ static const struct address_space_operations shmem_aops;
 static struct file_operations shmem_file_operations;
 static struct inode_operations shmem_inode_operations;
 static struct inode_operations shmem_dir_inode_operations;
+static struct inode_operations shmem_special_inode_operations;
 static struct vm_operations_struct shmem_vm_ops;
 
 static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
@@ -637,7 +640,7 @@ static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
         struct page *page = NULL;
         int error;
 
-        if (attr->ia_valid & ATTR_SIZE) {
+        if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
                 if (attr->ia_size < inode->i_size) {
                         /*
                          * If truncating down to a partial page, then
@@ -670,6 +673,10 @@ static int shmem_notify_change(struct dentry *dentry, struct iattr *attr)
         error = inode_change_ok(inode, attr);
         if (!error)
                 error = inode_setattr(inode, attr);
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        if (!error && (attr->ia_valid & ATTR_MODE))
+                error = generic_acl_chmod(inode, &shmem_acl_ops);
+#endif
         if (page)
                 page_cache_release(page);
         return error;
@@ -1362,6 +1369,7 @@ shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
 
                 switch (mode & S_IFMT) {
                 default:
+                        inode->i_op = &shmem_special_inode_operations;
                         init_special_inode(inode, mode, dev);
                         break;
                 case S_IFREG:
@@ -1682,7 +1690,11 @@ shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
                                 iput(inode);
                                 return error;
                         }
-                        error = 0;
+                }
+                error = shmem_acl_init(inode, dir);
+                if (error) {
+                        iput(inode);
+                        return error;
                 }
                 if (dir->i_mode & S_ISGID) {
                         inode->i_gid = dir->i_gid;
@@ -1897,6 +1909,53 @@ static struct inode_operations shmem_symlink_inode_operations = {
         .put_link       = shmem_put_link,
 };
 
+#ifdef CONFIG_TMPFS_POSIX_ACL
+/**
+ * Superblocks without xattr inode operations will get security.* xattr
+ * support from the VFS "for free". As soon as we have any other xattrs
+ * like ACLs, we also need to implement the security.* handlers at
+ * filesystem level, though.
+ */
+
+static size_t shmem_xattr_security_list(struct inode *inode, char *list,
+                                        size_t list_len, const char *name,
+                                        size_t name_len)
+{
+        return security_inode_listsecurity(inode, list, list_len);
+}
+
+static int shmem_xattr_security_get(struct inode *inode, const char *name,
+                                    void *buffer, size_t size)
+{
+        if (strcmp(name, "") == 0)
+                return -EINVAL;
+        return security_inode_getsecurity(inode, name, buffer, size,
+                                          -EOPNOTSUPP);
+}
+
+static int shmem_xattr_security_set(struct inode *inode, const char *name,
+                                    const void *value, size_t size, int flags)
+{
+        if (strcmp(name, "") == 0)
+                return -EINVAL;
+        return security_inode_setsecurity(inode, name, value, size, flags);
+}
+
+struct xattr_handler shmem_xattr_security_handler = {
+        .prefix = XATTR_SECURITY_PREFIX,
+        .list   = shmem_xattr_security_list,
+        .get    = shmem_xattr_security_get,
+        .set    = shmem_xattr_security_set,
+};
+
+static struct xattr_handler *shmem_xattr_handlers[] = {
+        &shmem_xattr_acl_access_handler,
+        &shmem_xattr_acl_default_handler,
+        &shmem_xattr_security_handler,
+        NULL
+};
+#endif
+
 static int shmem_parse_options(char *options, int *mode, uid_t *uid,
         gid_t *gid, unsigned long *blocks, unsigned long *inodes,
         int *policy, nodemask_t *policy_nodes)
@@ -2094,6 +2153,10 @@ static int shmem_fill_super(struct super_block *sb,
         sb->s_magic = TMPFS_MAGIC;
         sb->s_op = &shmem_ops;
         sb->s_time_gran = 1;
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        sb->s_xattr = shmem_xattr_handlers;
+        sb->s_flags |= MS_POSIXACL;
+#endif
 
         inode = shmem_get_inode(sb, S_IFDIR | mode, 0);
         if (!inode)
@@ -2130,6 +2193,7 @@ static void shmem_destroy_inode(struct inode *inode)
                 /* only struct inode is valid if it's an inline symlink */
                 mpol_free_shared_policy(&SHMEM_I(inode)->policy);
         }
+        shmem_acl_destroy_inode(inode);
         kmem_cache_free(shmem_inode_cachep, SHMEM_I(inode));
 }
 
@@ -2141,6 +2205,10 @@ static void init_once(void *foo, struct kmem_cache *cachep,
         if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
             SLAB_CTOR_CONSTRUCTOR) {
                 inode_init_once(&p->vfs_inode);
+#ifdef CONFIG_TMPFS_POSIX_ACL
+                p->i_acl = NULL;
+                p->i_default_acl = NULL;
+#endif
         }
 }
 
@@ -2184,6 +2252,14 @@ static struct inode_operations shmem_inode_operations = {
         .truncate       = shmem_truncate,
         .setattr        = shmem_notify_change,
         .truncate_range = shmem_truncate_range,
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        .setxattr       = generic_setxattr,
+        .getxattr       = generic_getxattr,
+        .listxattr      = generic_listxattr,
+        .removexattr    = generic_removexattr,
+        .permission     = shmem_permission,
+#endif
+
 };
 
 static struct inode_operations shmem_dir_inode_operations = {
@@ -2198,6 +2274,25 @@ static struct inode_operations shmem_dir_inode_operations = {
         .mknod          = shmem_mknod,
         .rename         = shmem_rename,
 #endif
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        .setattr        = shmem_notify_change,
+        .setxattr       = generic_setxattr,
+        .getxattr       = generic_getxattr,
+        .listxattr      = generic_listxattr,
+        .removexattr    = generic_removexattr,
+        .permission     = shmem_permission,
+#endif
+};
+
+static struct inode_operations shmem_special_inode_operations = {
+#ifdef CONFIG_TMPFS_POSIX_ACL
+        .setattr        = shmem_notify_change,
+        .setxattr       = generic_setxattr,
+        .getxattr       = generic_getxattr,
+        .listxattr      = generic_listxattr,
+        .removexattr    = generic_removexattr,
+        .permission     = shmem_permission,
+#endif
 };
 
 static struct super_operations shmem_ops = {
diff --git a/mm/shmem_acl.c b/mm/shmem_acl.c
new file mode 100644
index 000000000000..c946bf468718
--- /dev/null
+++ b/mm/shmem_acl.c
@@ -0,0 +1,197 @@
+/*
+ * mm/shmem_acl.c
+ *
+ * (C) 2005 Andreas Gruenbacher <agruen@suse.de>
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/fs.h>
+#include <linux/shmem_fs.h>
+#include <linux/xattr.h>
+#include <linux/generic_acl.h>
+
+/**
+ * shmem_get_acl  -   generic_acl_operations->getacl() operation
+ */
+static struct posix_acl *
+shmem_get_acl(struct inode *inode, int type)
+{
+        struct posix_acl *acl = NULL;
+
+        spin_lock(&inode->i_lock);
+        switch(type) {
+                case ACL_TYPE_ACCESS:
+                        acl = posix_acl_dup(SHMEM_I(inode)->i_acl);
+                        break;
+
+                case ACL_TYPE_DEFAULT:
+                        acl = posix_acl_dup(SHMEM_I(inode)->i_default_acl);
+                        break;
+        }
+        spin_unlock(&inode->i_lock);
+
+        return acl;
+}
+
+/**
+ * shmem_get_acl  -   generic_acl_operations->setacl() operation
+ */
+static void
+shmem_set_acl(struct inode *inode, int type, struct posix_acl *acl)
+{
+        struct posix_acl *free = NULL;
+
+        spin_lock(&inode->i_lock);
+        switch(type) {
+                case ACL_TYPE_ACCESS:
+                        free = SHMEM_I(inode)->i_acl;
+                        SHMEM_I(inode)->i_acl = posix_acl_dup(acl);
+                        break;
+
+                case ACL_TYPE_DEFAULT:
+                        free = SHMEM_I(inode)->i_default_acl;
+                        SHMEM_I(inode)->i_default_acl = posix_acl_dup(acl);
+                        break;
+        }
+        spin_unlock(&inode->i_lock);
+        posix_acl_release(free);
+}
+
+struct generic_acl_operations shmem_acl_ops = {
+        .getacl = shmem_get_acl,
+        .setacl = shmem_set_acl,
+};
+
+/**
+ * shmem_list_acl_access, shmem_get_acl_access, shmem_set_acl_access,
+ * shmem_xattr_acl_access_handler  -  plumbing code to implement the
+ * system.posix_acl_access xattr using the generic acl functions.
+ */
+
+static size_t
+shmem_list_acl_access(struct inode *inode, char *list, size_t list_size,
+                      const char *name, size_t name_len)
+{
+        return generic_acl_list(inode, &shmem_acl_ops, ACL_TYPE_ACCESS,
+                                list, list_size);
+}
+
+static int
+shmem_get_acl_access(struct inode *inode, const char *name, void *buffer,
+                     size_t size)
+{
+        if (strcmp(name, "") != 0)
+                return -EINVAL;
+        return generic_acl_get(inode, &shmem_acl_ops, ACL_TYPE_ACCESS, buffer,
+                               size);
+}
+
+static int
+shmem_set_acl_access(struct inode *inode, const char *name, const void *value,
+                     size_t size, int flags)
+{
+        if (strcmp(name, "") != 0)
+                return -EINVAL;
+        return generic_acl_set(inode, &shmem_acl_ops, ACL_TYPE_ACCESS, value,
+                               size);
+}
+
+struct xattr_handler shmem_xattr_acl_access_handler = {
+        .prefix = POSIX_ACL_XATTR_ACCESS,
+        .list   = shmem_list_acl_access,
+        .get    = shmem_get_acl_access,
+        .set    = shmem_set_acl_access,
+};
+
+/**
+ * shmem_list_acl_default, shmem_get_acl_default, shmem_set_acl_default,
+ * shmem_xattr_acl_default_handler  -  plumbing code to implement the
+ * system.posix_acl_default xattr using the generic acl functions.
+ */
+
+static size_t
+shmem_list_acl_default(struct inode *inode, char *list, size_t list_size,
+                       const char *name, size_t name_len)
+{
+        return generic_acl_list(inode, &shmem_acl_ops, ACL_TYPE_DEFAULT,
+                                list, list_size);
+}
+
+static int
+shmem_get_acl_default(struct inode *inode, const char *name, void *buffer,
+                      size_t size)
+{
+        if (strcmp(name, "") != 0)
+                return -EINVAL;
+        return generic_acl_get(inode, &shmem_acl_ops, ACL_TYPE_DEFAULT, buffer,
+                               size);
+}
+
+static int
+shmem_set_acl_default(struct inode *inode, const char *name, const void *value,
+                      size_t size, int flags)
+{
+        if (strcmp(name, "") != 0)
+                return -EINVAL;
+        return generic_acl_set(inode, &shmem_acl_ops, ACL_TYPE_DEFAULT, value,
+                               size);
+}
+
+struct xattr_handler shmem_xattr_acl_default_handler = {
+        .prefix = POSIX_ACL_XATTR_DEFAULT,
+        .list   = shmem_list_acl_default,
+        .get    = shmem_get_acl_default,
+        .set    = shmem_set_acl_default,
+};
+
+/**
+ * shmem_acl_init  -  Inizialize the acl(s) of a new inode
+ */
+int
+shmem_acl_init(struct inode *inode, struct inode *dir)
+{
+        return generic_acl_init(inode, dir, &shmem_acl_ops);
+}
+
+/**
+ * shmem_acl_destroy_inode  -  destroy acls hanging off the in-memory inode
+ *
+ * This is done before destroying the actual inode.
+ */
+
+void
+shmem_acl_destroy_inode(struct inode *inode)
+{
+        if (SHMEM_I(inode)->i_acl)
+                posix_acl_release(SHMEM_I(inode)->i_acl);
+        SHMEM_I(inode)->i_acl = NULL;
+        if (SHMEM_I(inode)->i_default_acl)
+                posix_acl_release(SHMEM_I(inode)->i_default_acl);
+        SHMEM_I(inode)->i_default_acl = NULL;
+}
+
+/**
+ * shmem_check_acl  -  check_acl() callback for generic_permission()
+ */
+static int
+shmem_check_acl(struct inode *inode, int mask)
+{
+        struct posix_acl *acl = shmem_get_acl(inode, ACL_TYPE_ACCESS);
+
+        if (acl) {
+                int error = posix_acl_permission(inode, acl, mask);
+                posix_acl_release(acl);
+                return error;
+        }
+        return -EAGAIN;
+}
+
+/**
+ * shmem_permission  -  permission() inode operation
+ */
+int
+shmem_permission(struct inode *inode, int mask, struct nameidata *nd)
+{
+        return generic_permission(inode, mask, shmem_check_acl);
+}