linux-kernel - Re: [PATCH 2/2] AppArmor: Fix lsm_get_self

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Date: Tue, 27 Feb 2024 17:13:58 -0500
From: Paul Moore <paul@...l-moore.com>
To: Mickaël Salaün <mic@...ikod.net>, 
	John Johansen <john.johansen@...onical.com>
Cc: Casey Schaufler <casey@...aufler-ca.com>, James Morris <jmorris@...ei.org>, 
	"Serge E . Hallyn" <serge@...lyn.com>, linux-kernel@...r.kernel.org, 
	linux-security-module@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 2/2] AppArmor: Fix lsm_get_self_attr()

On Tue, Feb 27, 2024 at 5:09 PM Paul Moore <paul@...l-moore.com> wrote:
> On Tue, Feb 27, 2024 at 11:01 AM Paul Moore <paul@...l-moore.com> wrote:
> > On Mon, Feb 26, 2024 at 2:59 PM Paul Moore <paul@...l-moore.com> wrote:
> > > On Fri, Feb 23, 2024 at 4:07 PM Paul Moore <paul@...l-moore.com> wrote:
> > > > On Fri, Feb 23, 2024 at 2:06 PM Mickaël Salaün <mic@...ikod.net> wrote:
> > > > >
> > > > > aa_getprocattr() may not initialize the value's pointer in some case.
> > > > > As for proc_pid_attr_read(), initialize this pointer to NULL in
> > > > > apparmor_getselfattr() to avoid an UAF in the kfree() call.
> > > > >
> > > > > Cc: Casey Schaufler <casey@...aufler-ca.com>
> > > > > Cc: John Johansen <john.johansen@...onical.com>
> > > > > Cc: Paul Moore <paul@...l-moore.com>
> > > > > Cc: stable@...r.kernel.org
> > > > > Fixes: 223981db9baf ("AppArmor: Add selfattr hooks")
> > > > > Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> > > > > ---
> > > > >  security/apparmor/lsm.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > If you like John, I can send this up to Linus with the related SELinux
> > > > fix, I would just need an ACK from you.
> > >
> > > Reviewed-by: Paul Moore <paul@...l-moore.com>
> > >
> > > This patch looks good to me, and while we've still got at least two
> > > (maybe three?) more weeks before v6.8 is tagged, I think it would be
> > > good to get this up to Linus ASAP.  I'll hold off for another day, but
> > > if we don't see any comment from John I'll go ahead and merge this and
> > > send it up to Linus with the SELinux fix; I'm sure John wouldn't be
> > > happy if v6.8 went out the door without this fix.
> >
> > I just merged this into lsm/stable-6.8 and once the automated
> > build/test has done it's thing and come back clean I'll send this,
> > along with the associated SELinux fix, up to Linus.  Thanks all.
>
> In off-list discussions with Mickaël today it was noted that this
> patch also needs a fixup to the commit description so I've replaced it
> with the following:
>
>   "In apparmor_getselfattr() when an invalid AppArmor
>    attribute is requested, or a value hasn't been explicitly
>    set for the requested attribute, the label passed to
>    aa_put_label() is not properly initialized which can cause
>    problems when the pointer value is non-NULL and AppArmor
>    attempts to drop a reference on the bogus label object."
>
> I've updated the commit in lsm/stable-6.8 and I'll be sending it to
> Linus shortly.
>
> > John, if this commit is problematic please let me know and I'll send a
> > fix or a revert.

I also just realized that both this patch and the SELinux have the
stable kernel marking which shouldn't be necessary as the LSM syscalls
are only present in the v6.8-rcX kernels.  I'm going to drop the
stable tagging, but leave the 'Fixes:' tag of course.

-- 
paul-moore.com