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From: Neil Horman <nhorman@tuxdriver.com>
To: linux-nfs@vger.kernel.org
Cc: Neil Horman <nhorman@tuxdriver.com>,
	Trond Myklebust <Trond.Myklebust@netapp.com>, security@kernel.org,
	Jeff Layton <jlayton@redhat.com>
Subject: [PATCH] nfs4: Ensure that ACL pages sent over NFS were not
	allocated from the slab (v2)
Date: Fri,  4 Mar 2011 16:09:20 -0500
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diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 78936a8..6e906af 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -51,6 +51,7 @@
 #include <linux/sunrpc/bc_xprt.h>
 #include <linux/xattr.h>
 #include <linux/utsname.h>
+#include <linux/mm.h>
 
 #include "nfs4_fs.h"
 #include "delegation.h"
@@ -3252,6 +3253,36 @@ static void buf_to_pages(const void *buf, size_t buflen,
 	}
 }
 
+static int buf_to_pages_noslab(const void *buf, size_t buflen,
+		struct page **pages, unsigned int *pgbase)
+{
+	struct page *newpage, **spages;
+	int rc = 0;
+	size_t len;
+	spages = pages;
+
+	do {
+		len = min(PAGE_CACHE_SIZE, buflen);
+		newpage = alloc_page(GFP_KERNEL);
+
+		if (newpage == NULL)
+			goto unwind;
+		memcpy(page_address(newpage), buf, len);
+                buf += len;
+                buflen -= len;
+		*(pages++) = newpage;
+		rc++;
+	} while (buflen != 0);
+
+	*pgbase = 0;
+	return rc;
+
+unwind:
+	for(; rc > 0; rc--)
+		__free_page(spages[rc-1]);
+	return -ENOMEM;
+}
+
 struct nfs4_cached_acl {
 	int cached;
 	size_t len;
@@ -3420,13 +3451,23 @@ static int __nfs4_proc_set_acl(struct inode *inode, const void *buf, size_t bufl
 		.rpc_argp	= &arg,
 		.rpc_resp	= &res,
 	};
-	int ret;
+	int ret, i;
 
 	if (!nfs4_server_supports_acls(server))
 		return -EOPNOTSUPP;
+	i = buf_to_pages_noslab(buf, buflen, arg.acl_pages, &arg.acl_pgbase);
+	if (i < 0)
+		return i;
 	nfs_inode_return_delegation(inode);
-	buf_to_pages(buf, buflen, arg.acl_pages, &arg.acl_pgbase);
 	ret = nfs4_call_sync(server, &msg, &arg, &res, 1);
+
+	/*
+	 * Free each page after tx, so the only ref left is 
+	 * held by the network stack
+	 */
+	for (; i > 0; i--)
+		put_page(pages[i-1]);
+
 	/*
 	 * Acl update can result in inode attribute update.
 	 * so mark the attribute cache invalid.