1 files changed, 146 insertions, 53 deletions

diff --git a/fs/xattr.c b/fs/xattr.c
index bcc2156d4d28..80eca7d3d69f 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -19,6 +19,149 @@
 #include <linux/fsnotify.h>
 #include <asm/uaccess.h>
 
+
+/*
+ * Check permissions for extended attribute access.  This is a bit complicated
+ * because different namespaces have very different rules.
+ */
+static int
+xattr_permission(struct inode *inode, const char *name, int mask)
+{
+        /*
+         * We can never set or remove an extended attribute on a read-only
+         * filesystem  or on an immutable / append-only inode.
+         */
+        if (mask & MAY_WRITE) {
+                if (IS_RDONLY(inode))
+                        return -EROFS;
+                if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
+                        return -EPERM;
+        }
+
+        /*
+         * No restriction for security.* and system.* from the VFS.  Decision
+         * on these is left to the underlying filesystem / security module.
+         */
+        if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
+            !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
+                return 0;
+
+        /*
+         * The trusted.* namespace can only accessed by a privilegued user.
+         */
+        if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
+                return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
+
+        if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
+                if (!S_ISREG(inode->i_mode) &&
+                    (!S_ISDIR(inode->i_mode) || inode->i_mode & S_ISVTX))
+                        return -EPERM;
+        }
+
+        return permission(inode, mask, NULL);
+}
+
+int
+vfs_setxattr(struct dentry *dentry, char *name, void *value,
+                size_t size, int flags)
+{
+        struct inode *inode = dentry->d_inode;
+        int error;
+
+        error = xattr_permission(inode, name, MAY_WRITE);
+        if (error)
+                return error;
+
+        mutex_lock(&inode->i_mutex);
+        error = security_inode_setxattr(dentry, name, value, size, flags);
+        if (error)
+                goto out;
+        error = -EOPNOTSUPP;
+        if (inode->i_op->setxattr) {
+                error = inode->i_op->setxattr(dentry, name, value, size, flags);
+                if (!error) {
+                        fsnotify_xattr(dentry);
+                        security_inode_post_setxattr(dentry, name, value,
+                                                     size, flags);
+                }
+        } else if (!strncmp(name, XATTR_SECURITY_PREFIX,
+                                XATTR_SECURITY_PREFIX_LEN)) {
+                const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
+                error = security_inode_setsecurity(inode, suffix, value,
+                                                   size, flags);
+                if (!error)
+                        fsnotify_xattr(dentry);
+        }
+out:
+        mutex_unlock(&inode->i_mutex);
+        return error;
+}
+EXPORT_SYMBOL_GPL(vfs_setxattr);
+
+ssize_t
+vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
+{
+        struct inode *inode = dentry->d_inode;
+        int error;
+
+        error = xattr_permission(inode, name, MAY_READ);
+        if (error)
+                return error;
+
+        error = security_inode_getxattr(dentry, name);
+        if (error)
+                return error;
+
+        if (inode->i_op->getxattr)
+                error = inode->i_op->getxattr(dentry, name, value, size);
+        else
+                error = -EOPNOTSUPP;
+
+        if (!strncmp(name, XATTR_SECURITY_PREFIX,
+                                XATTR_SECURITY_PREFIX_LEN)) {
+                const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
+                int ret = security_inode_getsecurity(inode, suffix, value,
+                                                     size, error);
+                /*
+                 * Only overwrite the return value if a security module
+                 * is actually active.
+                 */
+                if (ret != -EOPNOTSUPP)
+                        error = ret;
+        }
+
+        return error;
+}
+EXPORT_SYMBOL_GPL(vfs_getxattr);
+
+int
+vfs_removexattr(struct dentry *dentry, char *name)
+{
+        struct inode *inode = dentry->d_inode;
+        int error;
+
+        if (!inode->i_op->removexattr)
+                return -EOPNOTSUPP;
+
+        error = xattr_permission(inode, name, MAY_WRITE);
+        if (error)
+                return error;
+
+        error = security_inode_removexattr(dentry, name);
+        if (error)
+                return error;
+
+        mutex_lock(&inode->i_mutex);
+        error = inode->i_op->removexattr(dentry, name);
+        mutex_unlock(&inode->i_mutex);
+
+        if (!error)
+                fsnotify_xattr(dentry);
+        return error;
+}
+EXPORT_SYMBOL_GPL(vfs_removexattr);
+
+
 /*
  * Extended attribute SET operations
  */
@@ -51,29 +194,7 @@ setxattr(struct dentry *d, char __user *name, void __user *value,
                 }
         }
 
-        down(&d->d_inode->i_sem);
-        error = security_inode_setxattr(d, kname, kvalue, size, flags);
-        if (error)
-                goto out;
-        error = -EOPNOTSUPP;
-        if (d->d_inode->i_op && d->d_inode->i_op->setxattr) {
-                error = d->d_inode->i_op->setxattr(d, kname, kvalue,
-                                                   size, flags);
-                if (!error) {
-                        fsnotify_xattr(d);
-                        security_inode_post_setxattr(d, kname, kvalue,
-                                                     size, flags);
-                }
-        } else if (!strncmp(kname, XATTR_SECURITY_PREFIX,
-                            sizeof XATTR_SECURITY_PREFIX - 1)) {
-                const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1;
-                error = security_inode_setsecurity(d->d_inode, suffix, kvalue,
-                                                   size, flags);
-                if (!error)
-                        fsnotify_xattr(d);
-        }
-out:
-        up(&d->d_inode->i_sem);
+        error = vfs_setxattr(d, kname, kvalue, size, flags);
         kfree(kvalue);
         return error;
 }
@@ -147,22 +268,7 @@ getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
                         return -ENOMEM;
         }
 
-        error = security_inode_getxattr(d, kname);
-        if (error)
-                goto out;
-        error = -EOPNOTSUPP;
-        if (d->d_inode->i_op && d->d_inode->i_op->getxattr)
-                error = d->d_inode->i_op->getxattr(d, kname, kvalue, size);
-
-        if (!strncmp(kname, XATTR_SECURITY_PREFIX,
-                     sizeof XATTR_SECURITY_PREFIX - 1)) {
-                const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1;
-                int rv = security_inode_getsecurity(d->d_inode, suffix, kvalue,
-                                                    size, error);
-                /* Security module active: overwrite error value */
-                if (rv != -EOPNOTSUPP)
-                        error = rv;
-        }
+        error = vfs_getxattr(d, kname, kvalue, size);
         if (error > 0) {
                 if (size && copy_to_user(value, kvalue, error))
                         error = -EFAULT;
@@ -171,7 +277,6 @@ getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
                    than XATTR_SIZE_MAX bytes. Not possible. */
                 error = -E2BIG;
         }
-out:
         kfree(kvalue);
         return error;
 }
@@ -318,19 +423,7 @@ removexattr(struct dentry *d, char __user *name)
         if (error < 0)
                 return error;
 
-        error = -EOPNOTSUPP;
-        if (d->d_inode->i_op && d->d_inode->i_op->removexattr) {
-                error = security_inode_removexattr(d, kname);
-                if (error)
-                        goto out;
-                down(&d->d_inode->i_sem);
-                error = d->d_inode->i_op->removexattr(d, kname);
-                up(&d->d_inode->i_sem);
-                if (!error)
-                        fsnotify_xattr(d);
-        }
-out:
-        return error;
+        return vfs_removexattr(d, kname);
 }
 
 asmlinkage long