• David Windsor's avatar
    jfs: Define usercopy region in jfs_ip slab cache · 8d2704d3
    David Windsor authored
    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.
    
    cache object allocation:
        fs/jfs/super.c:
            jfs_alloc_inode(...):
                ...
                jfs_inode = kmem_cache_alloc(jfs_inode_cachep, GFP_NOFS);
                ...
                return &jfs_inode->vfs_inode;
    
        fs/jfs/jfs_incore.h:
            JFS_IP(struct inode *inode):
                return container_of(inode, struct jfs_inode_info, vfs_inode);
    
        fs/jfs/inode.c:
            jfs_iget(...):
                ...
                inode->i_link = JFS_IP(inode)->i_inline;
    
    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
    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 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: default avatarDavid Windsor <dave@nullcore.net>
    [kees: adjust commit log, provide usage trace]
    Cc: Dave Kleikamp <shaggy@kernel.org>
    Cc: jfs-discussion@lists.sourceforge.net
    Signed-off-by: default avatarKees Cook <keescook@chromium.org>
    Acked-by: default avatarDave Kleikamp <dave.kleikamp@oracle.com>
    8d2704d3
super.c 24.8 KB