lkml.org 
[lkml]   [2018]   [Jan]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 17/36] vxfs: Define usercopy region in vxfs_inode slab cache
    Date
    From: David Windsor <dave@nullcore.net>

    vxfs symlink pathnames, stored in struct vxfs_inode_info field
    vii_immed.vi_immed and therefore contained in the vxfs_inode slab cache,
    need to be copied to/from userspace.

    cache object allocation:
    fs/freevxfs/vxfs_super.c:
    vxfs_alloc_inode(...):
    ...
    vi = kmem_cache_alloc(vxfs_inode_cachep, GFP_KERNEL);
    ...
    return &vi->vfs_inode;

    fs/freevxfs/vxfs_inode.c:
    cxfs_iget(...):
    ...
    inode->i_link = vip->vii_immed.vi_immed;

    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
    vxfs_inode 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: Christoph Hellwig <hch@infradead.org>
    Signed-off-by: Kees Cook <keescook@chromium.org>
    ---
    fs/freevxfs/vxfs_super.c | 8 ++++++--
    1 file changed, 6 insertions(+), 2 deletions(-)

    diff --git a/fs/freevxfs/vxfs_super.c b/fs/freevxfs/vxfs_super.c
    index f989efa051a0..48b24bb50d02 100644
    --- a/fs/freevxfs/vxfs_super.c
    +++ b/fs/freevxfs/vxfs_super.c
    @@ -332,9 +332,13 @@ vxfs_init(void)
    {
    int rv;

    - vxfs_inode_cachep = kmem_cache_create("vxfs_inode",
    + vxfs_inode_cachep = kmem_cache_create_usercopy("vxfs_inode",
    sizeof(struct vxfs_inode_info), 0,
    - SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
    + SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD,
    + offsetof(struct vxfs_inode_info, vii_immed.vi_immed),
    + sizeof_field(struct vxfs_inode_info,
    + vii_immed.vi_immed),
    + NULL);
    if (!vxfs_inode_cachep)
    return -ENOMEM;
    rv = register_filesystem(&vxfs_fs_type);
    --
    2.7.4
    \
     
     \ /
      Last update: 2018-01-14 23:20    [W:2.267 / U:1.660 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site