linux-kernel - [PATCH 11/23] jfs: define usercopy region in jfs

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Message-Id: <1497915397-93805-12-git-send-email-keescook@chromium.org>
Date:   Mon, 19 Jun 2017 16:36:25 -0700
From:   Kees Cook <keescook@...omium.org>
To:     kernel-hardening@...ts.openwall.com
Cc:     Kees Cook <keescook@...omium.org>,
        David Windsor <dave@...lcore.net>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 11/23] jfs: define usercopy region in jfs_ip slab cache

From: David Windsor <dave@...lcore.net>

The jfs symlink pathnames, stored in struct jfs_inode_info.i_inline
and therefore contained in the jfs_ip slab cache, need to be copied to/from
userspace.

In support of usercopy hardening, this patch defines a region in
the jfs_ip slab cache in which userspace copy operations
are allowed.

This region is known as the slab cache's usercopy region.  Slab
caches can now check that each copy operation involving cache-managed
memory falls entirely within the slab's usercopy region.

This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.

Signed-off-by: David Windsor <dave@...lcore.net>
[kees: adjust commit log]
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 fs/jfs/super.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index e8aad7d87b8c..10b958f49f57 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -972,9 +972,11 @@ static int __init init_jfs_fs(void)
 	int rc;

 	jfs_inode_cachep =
-	    kmem_cache_create("jfs_ip", sizeof(struct jfs_inode_info), 0,
-			    SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
-			    init_once);
+	    kmem_cache_create_usercopy("jfs_ip", sizeof(struct jfs_inode_info),
+			0, SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|SLAB_ACCOUNT,
+			offsetof(struct jfs_inode_info, i_inline),
+			sizeof_field(struct jfs_inode_info, i_inline),
+			init_once);
 	if (jfs_inode_cachep == NULL)
 		return -ENOMEM;

-- 
2.7.4