linux-kernel - Re: [PATCH v2 1/6] LSM: Ensure the correct LSM context releaser

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Message-ID: <CAHC9VhQ0mBKz-y33+xV-de+hjA-wMbcv9+VmBXWiPjk5Ygz2eQ@mail.gmail.com>
Date: Tue, 22 Oct 2024 12:25:35 -0400
From: Paul Moore <paul@...l-moore.com>
To: Casey Schaufler <casey@...aufler-ca.com>
Cc: 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, selinux@...r.kernel.org, mic@...ikod.net, 
	linux-integrity@...r.kernel.org, netdev@...r.kernel.org, 
	audit@...r.kernel.org, netfilter-devel@...r.kernel.org, 
	linux-nfs@...r.kernel.org, Todd Kjos <tkjos@...gle.com>
Subject: Re: [PATCH v2 1/6] LSM: Ensure the correct LSM context releaser

On Mon, Oct 21, 2024 at 7:58 PM Casey Schaufler <casey@...aufler-ca.com> wrote:
> On 10/21/2024 4:39 PM, Paul Moore wrote:
> > On Oct 14, 2024 Casey Schaufler <casey@...aufler-ca.com> wrote:
> >> Add a new lsm_context data structure to hold all the information about a
> >> "security context", including the string, its size and which LSM allocated
> >> the string. The allocation information is necessary because LSMs have
> >> different policies regarding the lifecycle of these strings. SELinux
> >> allocates and destroys them on each use, whereas Smack provides a pointer
> >> to an entry in a list that never goes away.
> >>
> >> Update security_release_secctx() to use the lsm_context instead of a
> >> (char *, len) pair. Change its callers to do likewise.  The LSMs
> >> supporting this hook have had comments added to remind the developer
> >> that there is more work to be done.
> >>
> >> The BPF security module provides all LSM hooks. While there has yet to
> >> be a known instance of a BPF configuration that uses security contexts,
> >> the possibility is real. In the existing implementation there is
> >> potential for multiple frees in that case.
> >>
> >> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> >> Cc: linux-integrity@...r.kernel.org
> >> Cc: netdev@...r.kernel.org
> >> Cc: audit@...r.kernel.org
> >> Cc: netfilter-devel@...r.kernel.org
> >> To: Pablo Neira Ayuso <pablo@...filter.org>
> >> Cc: linux-nfs@...r.kernel.org
> >> Cc: Todd Kjos <tkjos@...gle.com>
> >> Reviewed-by: Serge Hallyn <sergeh@...nel.org>
> >> ---
> >>  drivers/android/binder.c                | 24 ++++++-------
> >>  fs/ceph/xattr.c                         |  6 +++-
> >>  fs/nfs/nfs4proc.c                       |  8 +++--
> >>  fs/nfsd/nfs4xdr.c                       |  8 +++--
> >>  include/linux/lsm_hook_defs.h           |  2 +-
> >>  include/linux/security.h                | 35 +++++++++++++++++--
> >>  include/net/scm.h                       | 11 +++---
> >>  kernel/audit.c                          | 30 ++++++++---------
> >>  kernel/auditsc.c                        | 23 +++++++------
> >>  net/ipv4/ip_sockglue.c                  | 10 +++---
> >>  net/netfilter/nf_conntrack_netlink.c    | 10 +++---
> >>  net/netfilter/nf_conntrack_standalone.c |  9 +++--
> >>  net/netfilter/nfnetlink_queue.c         | 13 ++++---
> >>  net/netlabel/netlabel_unlabeled.c       | 45 +++++++++++--------------
> >>  net/netlabel/netlabel_user.c            | 11 +++---
> >>  security/apparmor/include/secid.h       |  2 +-
> >>  security/apparmor/secid.c               | 11 ++++--
> >>  security/security.c                     |  8 ++---
> >>  security/selinux/hooks.c                | 11 ++++--
> >>  19 files changed, 167 insertions(+), 110 deletions(-)
> > ..
> >
> >> diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
> >> index 1bc2d0890a9f..8303bbcfc543 100644
> >> --- a/net/netlabel/netlabel_unlabeled.c
> >> +++ b/net/netlabel/netlabel_unlabeled.c
> >> @@ -1127,14 +1122,14 @@ static int netlbl_unlabel_staticlist_gen(u32 cmd,
> >>              secid = addr6->secid;
> >>      }
> >>
> >> -    ret_val = security_secid_to_secctx(secid, &secctx, &secctx_len);
> >> +    ret_val = security_secid_to_secctx(secid, &ctx.context, &ctx.len);
> >>      if (ret_val != 0)
> >>              goto list_cb_failure;
> >>      ret_val = nla_put(cb_arg->skb,
> >>                        NLBL_UNLABEL_A_SECCTX,
> >> -                      secctx_len,
> >> -                      secctx);
> >> -    security_release_secctx(secctx, secctx_len);
> >> +                      ctx.len,
> >> +                      ctx.context);
> > Nitpicky alignment issue; please keep the arguments aligned as they
> > are currently.
>
> Not a problem, although it looks like it's correct to me. I'll check to make sure.

Thanks.  It's likely just an oddity due to tabs rendering a bit odd in
the diff, I usually check that but maybe I didn't/forgot here.  Not a
major problem either way, I only mentioned it because I was commenting
on other patches in the series.

-- 
paul-moore.com