Re: [PATCH v19 0/4] overlayfs override_creds=off & nested get xattr fix

On Fri, Dec 3, 2021 at 10:38 AM Vivek Goyal [off-list ref] wrote:

On Wed, Nov 17, 2021 at 09:36:42AM +0200, Amir Goldstein wrote:

quoted

On Wed, Nov 17, 2021 at 3:58 AM David Anderson [off-list ref] wrote:

quoted

Mark Salyzyn (3):
  Add flags option to get xattr method paired to __vfs_getxattr
  overlayfs: handle XATTR_NOSECURITY flag for get xattr method
  overlayfs: override_creds=off option bypass creator_cred

Mark Salyzyn + John Stultz (1):
  overlayfs: inode_owner_or_capable called during execv

The first three patches address fundamental security issues that should
be solved regardless of the override_creds=off feature.

The fourth adds the feature depends on these other fixes.

By default, all access to the upper, lower and work directories is the
recorded mounter's MAC and DAC credentials.  The incoming accesses are
checked against the caller's credentials.

If the principles of least privilege are applied for sepolicy, the
mounter's credentials might not overlap the credentials of the caller's
when accessing the overlayfs filesystem.  For example, a file that a
lower DAC privileged caller can execute, is MAC denied to the
generally higher DAC privileged mounter, to prevent an attack vector.

We add the option to turn off override_creds in the mount options; all
subsequent operations after mount on the filesystem will be only the
caller's credentials.  The module boolean parameter and mount option
override_creds is also added as a presence check for this "feature",
existence of /sys/module/overlay/parameters/overlay_creds

BTW, where is patch 1 of the series. I can't seem to find it.

Lore to the rescue ...

https://lore.kernel.org/selinux/20211117015806.2192263-2-dvander@google.com/ (local)

-- 
paul moore
www.paul-moore.com