linux-kernel - Re: [PATCH] security: fix the default value of secid_to

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Date:   Sat, 16 May 2020 10:04:58 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     James Morris <jamorris@...ux.microsoft.com>,
        Anders Roxell <anders.roxell@...aro.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        LKML <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH] security: fix the default value of secid_to_secctx hook

On Sat, May 16, 2020 at 1:29 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Thu, May 14, 2020 at 12:47 PM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > On Thu, May 14, 2020 at 12:43 PM James Morris
> > <jamorris@...ux.microsoft.com> wrote:
> > >
> > > On Wed, 13 May 2020, Alexei Starovoitov wrote:
> > >
> > > > James,
> > > >
> > > > since you took the previous similar patch are you going to pick this
> > > > one up as well?
> > > > Or we can route it via bpf tree to Linus asap.
> > >
> > > Routing via your tree is fine.
> >
> > Perfect.
> > Applied to bpf tree. Thanks everyone.
>
> Looks like it was a wrong fix.
> It breaks audit like this:
> sudo auditctl -e 0
> [   88.400296] audit: error in audit_log_task_context
> [   88.400976] audit: error in audit_log_task_context
> [   88.401597] audit: type=1305 audit(1589584951.198:89): op=set
> audit_enabled=0 old=1 auid=0 ses=1 res=0
> [   88.402691] audit: type=1300 audit(1589584951.198:89):
> arch=c000003e syscall=44 success=yes exit=52 a0=3 a1=7ffe42a37400
> a2=34 a3=0 items=0 ppid=2250 pid=2251 auid=0 uid=0 gid=0 euid=0 suid=0
> fsuid=0 egid=0 sgid=0 fsgid=0 tty=ttyS0 se)
> [   88.405587] audit: type=1327 audit(1589584951.198:89):
> proctitle=617564697463746C002D650030
> Error sending enable request (Operation not supported)
>
> when CONFIG_LSM= has "bpf" in it.

Do you have more than one LSM enabled? It looks like
the problem with security_secid_to_secctx() is now that it
returns an error if any of the LSMs fail and the caller expects
it to succeed if at least one of them sets the secdata pointer.

The problem earlier was that the call succeeded even though
no LSM had set the pointer.

What is the behavior we actually expect from this function if
multiple LSM are loaded?

       Arnd