[PATCH] add vfs_* helpers for xattr operations

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.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: James Morris <jmorris@namei.org>

(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?)

For NFSv4: instead of just converting it add an nfsd_getxattr helper for the
code shared by NFSv2/3 and NFSv4 ACLs.  In fact that code isn't even
NFS-specific, but I'll wait for more users to pop up first before moving it to
common code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Dave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Neil Brown <neilb@suse.de>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nfsd/vfs.c

@@ -48,8 +48,8 @@
 #include <linux/fsnotify.h>
 #include <linux/posix_acl.h>
 #include <linux/posix_acl_xattr.h>
-#ifdef CONFIG_NFSD_V4
 #include <linux/xattr.h>
+#ifdef CONFIG_NFSD_V4
 #include <linux/nfs4.h>
 #include <linux/nfs4_acl.h>
 #include <linux/nfsd_idmap.h>
@@ -365,8 +365,30 @@ out_nfserr:
 	goto out;
 }
 
-#if defined(CONFIG_NFSD_V4)
+#if defined(CONFIG_NFSD_V2_ACL) || \
+    defined(CONFIG_NFSD_V3_ACL) || \
+    defined(CONFIG_NFSD_V4)
+static ssize_t nfsd_getxattr(struct dentry *dentry, char *key, void **buf)
+{
+	ssize_t buflen;
+	int error;
+
+	buflen = vfs_getxattr(dentry, key, NULL, 0);
+	if (buflen <= 0)
+		return buflen;
 
+	*buf = kmalloc(buflen, GFP_KERNEL);
+	if (!*buf)
+		return -ENOMEM;
+
+	error = vfs_getxattr(dentry, key, *buf, buflen);
+	if (error < 0)
+		return error;
+	return buflen;
+}
+#endif
+
+#if defined(CONFIG_NFSD_V4)
 static int
 set_nfsv4_acl_one(struct dentry *dentry, struct posix_acl *pacl, char *key)
 {
@@ -374,7 +396,6 @@ set_nfsv4_acl_one(struct dentry *dentry, struct posix_acl *pacl, char *key)
 	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);
@@ -388,15 +409,7 @@ set_nfsv4_acl_one(struct dentry *dentry, struct posix_acl *pacl, char *key)
 		goto out;
 	}
 
-	error = -EOPNOTSUPP;
-	if (inode->i_op && inode->i_op->setxattr) {
-		mutex_lock(&inode->i_mutex);
-		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);
-		mutex_unlock(&inode->i_mutex);
-	}
+	error = vfs_setxattr(dentry, key, buf, len, 0);
 out:
 	kfree(buf);
 	return error;
@@ -455,44 +468,19 @@ out_nfserr:
 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;
+	void *buf = NULL;
 	struct posix_acl *pacl = NULL;
+	int buflen;
 
-	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);
-	if (buflen <= 0) {
-		error = buflen < 0 ? buflen : -ENODATA;
-		goto out_err;
-	}
-
-	buf = kmalloc(buflen, GFP_KERNEL);
-	if (buf == NULL) {
-		error = -ENOMEM;
-		goto out_err;
-	}
-
-	error = inode->i_op->getxattr(dentry, key, buf, buflen);
-	if (error < 0)
-		goto out_err;
+	buflen = nfsd_getxattr(dentry, key, &buf);
+	if (!buflen)
+		buflen = -ENODATA;
+	if (buflen <= 0)
+		return ERR_PTR(buflen);
 
 	pacl = posix_acl_from_xattr(buf, buflen);
- out:
 	kfree(buf);
 	return pacl;
- out_err:
-	pacl = ERR_PTR(error);
-	goto out;
 }
 
 int
@@ -1884,9 +1872,10 @@ nfsd_get_posix_acl(struct svc_fh *fhp, int type)
 	ssize_t size;
 	struct posix_acl *acl;
 
-	if (!IS_POSIXACL(inode) || !inode->i_op || !inode->i_op->getxattr)
+	if (!IS_POSIXACL(inode))
 		return ERR_PTR(-EOPNOTSUPP);
-	switch(type) {
+
+	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name = POSIX_ACL_XATTR_ACCESS;
 		break;
@@ -1897,26 +1886,11 @@ nfsd_get_posix_acl(struct svc_fh *fhp, int type)
 		return ERR_PTR(-EOPNOTSUPP);
 	}
 
-	size = inode->i_op->getxattr(fhp->fh_dentry, name, NULL, 0);
+	size = nfsd_getxattr(fhp->fh_dentry, name, &value);
+	if (size < 0)
+		return ERR_PTR(size);
 
-	if (size < 0) {
-		acl = ERR_PTR(size);
-		goto getout;
-	} else if (size > 0) {
-		value = kmalloc(size, GFP_KERNEL);
-		if (!value) {
-			acl = ERR_PTR(-ENOMEM);
-			goto getout;
-		}
-		size = inode->i_op->getxattr(fhp->fh_dentry, name, value, size);
-		if (size < 0) {
-			acl = ERR_PTR(size);
-			goto getout;
-		}
-	}
 	acl = posix_acl_from_xattr(value, size);
-
-getout:
 	kfree(value);
 	return acl;
 }
@@ -1957,16 +1931,13 @@ nfsd_set_posix_acl(struct svc_fh *fhp, int type, struct posix_acl *acl)
 	} else
 		size = 0;
 
-	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;
 		}

fs/xattr.c

@@ -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;
+
+	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,
+				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:
+	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 = 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;
+
+	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 +141,7 @@ setxattr(struct dentry *d, char __user *name, void __user *value,
 		}
 	}
 
-	mutex_lock(&d->d_inode->i_mutex);
-	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:
-	mutex_unlock(&d->d_inode->i_mutex);
+	error = vfs_setxattr(d, kname, kvalue, size, flags);
 	kfree(kvalue);
 	return error;
 }
@@ -147,22 +215,7 @@ 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 +224,6 @@ 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 +370,7 @@ 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;
-		mutex_lock(&d->d_inode->i_mutex);
-		error = d->d_inode->i_op->removexattr(d, kname);
-		mutex_unlock(&d->d_inode->i_mutex);
-		if (!error)
-			fsnotify_xattr(d);
-	}
-out:
-	return error;
+	return vfs_removexattr(d, kname);
 }
 
 asmlinkage long

include/linux/xattr.h

@@ -25,6 +25,10 @@ struct xattr_handler {
 		   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);