Techwizz/kernel-fxtec-pro1x
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

befs: Define usercopy region in befs_inode_cache slab cache

Browse source 
befs symlink pathnames, stored in struct befs_inode_info.i_data.symlink
and therefore contained in the befs_inode_cache slab cache, need to be
copied to/from userspace.

cache object allocation:
    fs/befs/linuxvfs.c:
        befs_alloc_inode(...):
            ...
            bi = kmem_cache_alloc(befs_inode_cachep, GFP_KERNEL);
            ...
            return &bi->vfs_inode;

        befs_iget(...):
            ...
            strlcpy(befs_ino->i_data.symlink, raw_inode->data.symlink,
                    BEFS_SYMLINK_LEN);
            ...
            inode->i_link = befs_ino->i_data.symlink;

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
befs_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 <dave@nullcore.net>
[kees: adjust commit log, provide usage trace]
Cc: Luis de Bethencourt <luisbg@kernel.org>
Cc: Salah Triki <salah.triki@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Luis de Bethencourt <luisbg@kernel.org>
This commit is contained in:
David Windsor 2017-06-10 22:50:32 -04:00 committed by Kees Cook
parent 8d2704d382
commit 0fc256d3ad
1 changed files with 9 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

14
fs/befs/linuxvfs.c
View file

@ -444,11 +444,15 @@ static struct inode *befs_iget(struct super_block *sb, unsigned long ino)
static int __init
befs_init_inodecache(void)
{
befs_inode_cachep = kmem_cache_create("befs_inode_cache",
sizeof (struct befs_inode_info),
0, (SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD|SLAB_ACCOUNT),
init_once);
befs_inode_cachep = kmem_cache_create_usercopy("befs_inode_cache",
sizeof(struct befs_inode_info), 0,
(SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD|
SLAB_ACCOUNT),
offsetof(struct befs_inode_info,
i_data.symlink),
sizeof_field(struct befs_inode_info,
i_data.symlink),
init_once);
if (befs_inode_cachep == NULL)
return -ENOMEM;