On Mon, Sep 26, 2022 at 10:09 AM Christian Brauner <brauner@xxxxxxxxxx> wrote: > > The current way of setting and getting posix acls through the generic > xattr interface is error prone and type unsafe. The vfs needs to > interpret and fixup posix acls before storing or reporting it to > userspace. Various hacks exist to make this work. The code is hard to > understand and difficult to maintain in it's current form. Instead of > making this work by hacking posix acls through xattr handlers we are > building a dedicated posix acl api around the get and set inode > operations. This removes a lot of hackiness and makes the codepaths > easier to maintain. A lot of background can be found in [1]. > > So far posix acls were passed as a void blob to the security and > integrity modules. Some of them like evm then proceed to interpret the > void pointer and convert it into the kernel internal struct posix acl > representation to perform their integrity checking magic. This is > obviously pretty problematic as that requires knowledge that only the > vfs is guaranteed to have and has lead to various bugs. Add a proper > security hook for setting posix acls and pass down the posix acls in > their appropriate vfs format instead of hacking it through a void > pointer stored in the uapi format. > > In the next patches we implement the hooks for the few security modules > that do actually have restrictions on posix acls. > > Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@xxxxxxxxxx [1] > Signed-off-by: Christian Brauner (Microsoft) <brauner@xxxxxxxxxx> > --- > > Notes: > /* v2 */ > unchanged > > include/linux/lsm_hook_defs.h | 2 ++ > include/linux/lsm_hooks.h | 4 ++++ > include/linux/security.h | 11 +++++++++++ > security/security.c | 9 +++++++++ > 4 files changed, 26 insertions(+) The only thing that is really absent from the new hook, compared to the existing security_inode_setxattr() hook in the ACL case, is the EVM hook which looks to be addressed in patch 13/30. Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx> -- paul-moore.com
