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From:   Paul Moore <paul@paul-moore.com>
Date:   Wed, 9 Nov 2022 15:22:14 -0500
Message-ID: <CAHC9VhS9h2ZL=JZOoNK7Q+TDU7BSq3Jk2BqZ0nZExCfTvkuUuQ@mail.gmail.com>
Subject: Re: [GIT PULL] LSM fixes for v6.1 (#1)
To:     "Serge E. Hallyn" <serge@hallyn.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
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On Wed, Nov 9, 2022 at 3:13 PM Paul Moore <paul@paul-moore.com> wrote:
> On Wed, Nov 9, 2022 at 9:38 AM Serge E. Hallyn <serge@hallyn.com> wrote:
> > On Mon, Oct 31, 2022 at 12:22:29PM -0700, Linus Torvalds wrote:
> > > On Mon, Oct 31, 2022 at 4:07 AM Paul Moore <paul@paul-moore.com> wrote:
> > > >
> > > > A single patch to the capabilities code to fix a potential memory leak
> > > > in the xattr allocation error handling.  Please apply for v6.1-rcX.
> > >
> > > Pulled.
> > >
> > > However, I react to the strange test condition. Sure, it's
> > > pre-existing, but does it really make sense?
> > >
> > > It does
> > >
> > > +       if (ret < 0 || !tmpbuf) {
> > > +               size = ret;
> > > +               goto out_free;
> > > +       }
> > >
> > > and how the heck can 'tmpbuf' be NULL if vfs_getxattr_alloc() succeeded?
> >
> > I had to go through the history a bit - the !tmpbuf check was added
> >
> > https://www.spinics.net/lists/stable/msg463010.html
> >
> > because of a gcc warning.  Perhaps there's a better way to tell gcc
> > that it can't remain NULL if ret was < 0 ?
>
> Ooof, that's ugly, but thanks for digging it up.  As it turns out I
> happen to be working on a patch for vfs_getxattr_alloc() to fix the
> return value type right now, but it looks like I'll leave that gcc
> hack in place ... although I might leave a comment about it so the
> next person doesn't have to wonder.

Actually, it looks like there are other similar conditions, e.g.
evm_is_immutable(), without such a check and my compiler (gcc v12.2.0)
seems okay with it; presumably they fixed the compiler bug?

I guess I'll leave the hack in place for commoncap.c but not propagate
it elsewhere.

-- 
paul-moore.com