From 2b06a9e336170d7e3c807c21d5cd85cbc92fff4e Mon Sep 17 00:00:00 2001 From: David Windsor Date: Sat, 10 Jun 2017 22:50:34 -0400 Subject: exofs: Define usercopy region in exofs_inode_cache slab cache The exofs short symlink names, stored in struct exofs_i_info.i_data and therefore contained in the exofs_inode_cache slab cache, need to be copied to/from userspace. cache object allocation: fs/exofs/super.c: exofs_alloc_inode(...): ... oi = kmem_cache_alloc(exofs_inode_cachep, GFP_KERNEL); ... return &oi->vfs_inode; fs/exofs/namei.c: exofs_symlink(...): ... inode->i_link = (char *)oi->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 in 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 exofs_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: Boaz Harrosh Signed-off-by: Kees Cook --- fs/exofs/super.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'fs/exofs') diff --git a/fs/exofs/super.c b/fs/exofs/super.c index 819624cfc8da..e5c532875bb7 100644 --- a/fs/exofs/super.c +++ b/fs/exofs/super.c @@ -192,10 +192,13 @@ static void exofs_init_once(void *foo) */ static int init_inodecache(void) { - exofs_inode_cachep = kmem_cache_create("exofs_inode_cache", + exofs_inode_cachep = kmem_cache_create_usercopy("exofs_inode_cache", sizeof(struct exofs_i_info), 0, SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD | - SLAB_ACCOUNT, exofs_init_once); + SLAB_ACCOUNT, + offsetof(struct exofs_i_info, i_data), + sizeof_field(struct exofs_i_info, i_data), + exofs_init_once); if (exofs_inode_cachep == NULL) return -ENOMEM; return 0; -- cgit