linux-kernel - Re: [PATCH v14 4/11] LSM: syscalls for current process attributes

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Message-ID: <CAHC9VhSSRieK4tuVpOYkWT9UAwbkLZtVABZQFcsJrZnwCH9MhA@mail.gmail.com>
Date:   Thu, 7 Sep 2023 11:43:13 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     Casey Schaufler <casey@...aufler-ca.com>,
        linux-security-module@...r.kernel.org, jmorris@...ei.org,
        serge@...lyn.com, keescook@...omium.org,
        john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
        stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org
Subject: Re: [PATCH v14 4/11] LSM: syscalls for current process attributes

On Thu, Sep 7, 2023 at 11:37 AM Mickaël Salaün <mic@...ikod.net> wrote:
> On Wed, Sep 06, 2023 at 04:48:04PM -0700, Casey Schaufler wrote:
> > On 9/6/2023 4:22 PM, Paul Moore wrote:
> > > On Aug 28, 2023 Casey Schaufler <casey@...aufler-ca.com> wrote:
> > >> Create a system call lsm_get_self_attr() to provide the security
> > >> module maintained attributes of the current process.
> > >> Create a system call lsm_set_self_attr() to set a security
> > >> module maintained attribute of the current process.
> > >> Historically these attributes have been exposed to user space via
> > >> entries in procfs under /proc/self/attr.
> > >>
> > >> The attribute value is provided in a lsm_ctx structure. The structure
> > >> identifies the size of the attribute, and the attribute value. The format
> > >> of the attribute value is defined by the security module. A flags field
> > >> is included for LSM specific information. It is currently unused and must
> > >> be 0. The total size of the data, including the lsm_ctx structure and any
> > >> padding, is maintained as well.
> > >>
> > >> struct lsm_ctx {
> > >>         __u64 id;
> > >>         __u64 flags;
> > >>         __u64 len;
> > >>         __u64 ctx_len;
> > >>         __u8 ctx[];
> > >> };
> > >>
> > >> Two new LSM hooks are used to interface with the LSMs.
> > >> security_getselfattr() collects the lsm_ctx values from the
> > >> LSMs that support the hook, accounting for space requirements.
> > >> security_setselfattr() identifies which LSM the attribute is
> > >> intended for and passes it along.
> > >>
> > >> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> > >> Reviewed-by: Kees Cook <keescook@...omium.org>
> > >> Reviewed-by: Serge Hallyn <serge@...lyn.com>
> > >> Reviewed-by: John Johansen <john.johansen@...onical.com>
> > >> ---
>
> > >> +int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx,
> > >> +                   size_t __user *size, u32 flags)
> > >> +{
> > >> +  struct security_hook_list *hp;
> > >> +  struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, };
> > >> +  u8 __user *base = (u8 __user *)uctx;
> > >> +  size_t total = 0;
> > >> +  size_t entrysize;
> > >> +  size_t left;
> > >> +  bool toobig = false;
> > >> +  bool single = false;
> > >> +  int count = 0;
> > >> +  int rc;
> > >> +
> > >> +  if (attr == LSM_ATTR_UNDEF)
> > >> +          return -EINVAL;
> > >> +  if (size == NULL)
> > >> +          return -EINVAL;
> > >> +  if (get_user(left, size))
> > >> +          return -EFAULT;
> > >> +
> > >> +  if (flags) {
> > >> +          /*
> > >> +           * Only flag supported is LSM_FLAG_SINGLE
> > >> +           */
> > >> +          if (flags & LSM_FLAG_SINGLE)
> > >> +                  return -EINVAL;
> > > Should this be something like the following?
> > >
> > >   if (flags & ~LSM_FLAG_SINGLE)
> > >     return -EINVAL;
> >
> > Yes. I have a fix ready. There are a couple other touch-ups, too.
>
> This is already part of patch 11. It should be squashed here.

So it is, yes, patch 11 should only be selftest code.

-- 
paul-moore.com