[PATCH 1/8] add vfs_* helpers for xattr operations

[Christoph Hellwig <hch@lst.de>]

Add vfs_getxattr, vfs_setxattr and vfs_removexattr helpers for common
checks around invocation of the xattr methods.  NFSD already was missing
some of the checks and there will be more soon.

James, I haven't touched selinux yet because it's doing various odd
things and I'm not sure how it would interact with the security
attribute fallbacks you added.  Could you investigate whether it could
use vfs_getxattr or if not add a __vfs_getxattr helper to share the bits
it is fine with?


Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: linux-2.6/fs/nfsd/vfs.c
===================================================================
--- linux-2.6.orig/fs/nfsd/vfs.c	2005-10-31 14:34:22.000000000 +0100
+++ linux-2.6/fs/nfsd/vfs.c	2005-10-31 14:34:33.000000000 +0100
@@ -367,7 +367,6 @@
 	size_t buflen;
 	char *buf = NULL;
 	int error = 0;
-	struct inode *inode = dentry->d_inode;
 
 	buflen = posix_acl_xattr_size(pacl->a_count);
 	buf = kmalloc(buflen, GFP_KERNEL);
@@ -381,15 +380,7 @@
 		goto out;
 	}
 
-	error = -EOPNOTSUPP;
-	if (inode->i_op && inode->i_op->setxattr) {
-		down(&inode->i_sem);
-		security_inode_setxattr(dentry, key, buf, len, 0);
-		error = inode->i_op->setxattr(dentry, key, buf, len, 0);
-		if (!error)
-			security_inode_post_setxattr(dentry, key, buf, len, 0);
-		up(&inode->i_sem);
-	}
+	error = vfs_setxattr(dentry, key, buf, len, 0);
 out:
 	kfree(buf);
 	return error;
@@ -448,44 +439,32 @@
 static struct posix_acl *
 _get_posix_acl(struct dentry *dentry, char *key)
 {
-	struct inode *inode = dentry->d_inode;
 	char *buf = NULL;
 	int buflen, error = 0;
 	struct posix_acl *pacl = NULL;
 
-	error = -EOPNOTSUPP;
-	if (inode->i_op == NULL)
-		goto out_err;
-	if (inode->i_op->getxattr == NULL)
-		goto out_err;
-
-	error = security_inode_getxattr(dentry, key);
-	if (error)
-		goto out_err;
-
-	buflen = inode->i_op->getxattr(dentry, key, NULL, 0);
+	buflen = vfs_getxattr(dentry, key, NULL, 0);
 	if (buflen <= 0) {
-		error = buflen < 0 ? buflen : -ENODATA;
-		goto out_err;
+		pacl = ERR_PTR(buflen < 0 ? buflen : -ENODATA);
+		goto out;
 	}
 
 	buf = kmalloc(buflen, GFP_KERNEL);
 	if (buf == NULL) {
-		error = -ENOMEM;
-		goto out_err;
+		pacl = ERR_PTR(-ENOMEM);
+		goto out;
 	}
 
-	error = inode->i_op->getxattr(dentry, key, buf, buflen);
-	if (error < 0)
-		goto out_err;
+	error = vfs_getxattr(dentry, key, buf, buflen);
+	if (error < 0) {
+		pacl = ERR_PTR(error);
+		goto out;
+	}
 
 	pacl = posix_acl_from_xattr(buf, buflen);
  out:
 	kfree(buf);
 	return pacl;
- out_err:
-	pacl = ERR_PTR(error);
-	goto out;
 }
 
 int
@@ -1943,13 +1922,12 @@
 	if (!fhp->fh_locked)
 		fh_lock(fhp);  /* unlocking is done automatically */
 	if (size)
-		error = inode->i_op->setxattr(fhp->fh_dentry, name,
-					      value, size, 0);
+		error = vfs_setxattr(fhp->fh_dentry, name, value, size, 0);
 	else {
 		if (!S_ISDIR(inode->i_mode) && type == ACL_TYPE_DEFAULT)
 			error = 0;
 		else {
-			error = inode->i_op->removexattr(fhp->fh_dentry, name);
+			error = vfs_removexattr(fhp->fh_dentry, name);
 			if (error == -ENODATA)
 				error = 0;
 		}
Index: linux-2.6/fs/xattr.c
===================================================================
--- linux-2.6.orig/fs/xattr.c	2005-10-31 14:34:22.000000000 +0100
+++ linux-2.6/fs/xattr.c	2005-10-31 14:42:26.000000000 +0100
@@ -19,6 +19,96 @@
 #include <linux/fsnotify.h>
 #include <asm/uaccess.h>
 
+
+int
+vfs_setxattr(struct dentry *dentry, char *name, void *value,
+		size_t size, int flags)
+{
+	struct inode *inode = dentry->d_inode;
+	int error;
+
+	down(&inode->i_sem);
+	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,
+				sizeof XATTR_SECURITY_PREFIX - 1)) {
+		const char *suffix = name + sizeof XATTR_SECURITY_PREFIX - 1;
+		error = security_inode_setsecurity(inode, suffix, value,
+						   size, flags);
+		if (!error)
+			fsnotify_xattr(dentry);
+	}
+out:
+	up(&inode->i_sem);
+	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 = 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,
+				sizeof XATTR_SECURITY_PREFIX - 1)) {
+		const char *suffix = name + sizeof XATTR_SECURITY_PREFIX - 1;
+		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 = security_inode_removexattr(dentry, name);
+	if (error)
+		return error;
+
+	down(&inode->i_sem);
+	error = inode->i_op->removexattr(dentry, name);
+	up(&inode->i_sem);
+
+	if (!error)
+		fsnotify_xattr(dentry);
+	return error;
+}
+EXPORT_SYMBOL_GPL(vfs_removexattr);
+
+
 /*
  * Extended attribute SET operations
  */
@@ -51,29 +141,8 @@
 		}
 	}
 
-	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);
+
 	if (kvalue)
 		kfree(kvalue);
 	return error;
@@ -148,22 +217,7 @@
 			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;
@@ -172,7 +226,7 @@
 		   than XATTR_SIZE_MAX bytes. Not possible. */
 		error = -E2BIG;
 	}
-out:
+
 	if (kvalue)
 		kfree(kvalue);
 	return error;
@@ -321,19 +375,7 @@
 	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
Index: linux-2.6/include/linux/xattr.h
===================================================================
--- linux-2.6.orig/include/linux/xattr.h	2005-10-31 14:34:22.000000000 +0100
+++ linux-2.6/include/linux/xattr.h	2005-10-31 14:42:12.000000000 +0100
@@ -25,6 +25,10 @@
 		   size_t size, int flags);
 };
 
+ssize_t vfs_getxattr(struct dentry *, char *, void *, size_t);
+int vfs_setxattr(struct dentry *, char *, void *, size_t, int);
+int vfs_removexattr(struct dentry *, char *);
+
 ssize_t generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size);
 ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size);
 int generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags);