From 85212d4e04c345ccebb92b3afb4c978a0db56c56 Mon Sep 17 00:00:00 2001 From: David Windsor Date: Sat, 10 Jun 2017 22:50:35 -0400 Subject: ext2: Define usercopy region in ext2_inode_cache slab cache The ext2 symlink pathnames, stored in struct ext2_inode_info.i_data and therefore contained in the ext2_inode_cache slab cache, need to be copied to/from userspace. cache object allocation: fs/ext2/super.c: ext2_alloc_inode(...): struct ext2_inode_info *ei; ... ei = kmem_cache_alloc(ext2_inode_cachep, GFP_NOFS); ... return &ei->vfs_inode; fs/ext2/ext2.h: EXT2_I(struct inode *inode): return container_of(inode, struct ext2_inode_info, vfs_inode); fs/ext2/namei.c: ext2_symlink(...): ... inode->i_link = (char *)&EXT2_I(inode)->i_data; example usage trace: readlink_copy+0x43/0x70 vfs_readlink+0x62/0x110 SyS_readlinkat+0x100/0x130 fs/namei.c: readlink_copy(..., link): ... copy_to_user(..., link, len); (inlined into vfs_readlink) generic_readlink(dentry, ...): struct inode *inode = d_inode(dentry); const char *link = inode->i_link; ... readlink_copy(..., link); In support of usercopy hardening, this patch defines a region in the ext2_inode_cache 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 dynamically sized 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 [kees: adjust commit log, provide usage trace] Cc: Jan Kara Cc: linux-ext4@vger.kernel.org Signed-off-by: Kees Cook Acked-by: Jan Kara --- fs/ext2/super.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'fs/ext2/super.c') diff --git a/fs/ext2/super.c b/fs/ext2/super.c index 7646818ab266..50b8946c3d1a 100644 --- a/fs/ext2/super.c +++ b/fs/ext2/super.c @@ -220,11 +220,13 @@ static void init_once(void *foo) static int __init init_inodecache(void) { - ext2_inode_cachep = kmem_cache_create("ext2_inode_cache", - sizeof(struct ext2_inode_info), - 0, (SLAB_RECLAIM_ACCOUNT| - SLAB_MEM_SPREAD|SLAB_ACCOUNT), - init_once); + ext2_inode_cachep = kmem_cache_create_usercopy("ext2_inode_cache", + sizeof(struct ext2_inode_info), 0, + (SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD| + SLAB_ACCOUNT), + offsetof(struct ext2_inode_info, i_data), + sizeof_field(struct ext2_inode_info, i_data), + init_once); if (ext2_inode_cachep == NULL) return -ENOMEM; return 0; -- cgit v1.2.3