[PATCH] security: fix the default value of secid_to_secctx hook

[Schaufler, Casey]

> -----Original Message-----
> From: linux-kernel-owner at vger.kernel.org <linux-kernel-
> owner at vger.kernel.org> On Behalf Of Arnd Bergmann
> Sent: Saturday, May 16, 2020 1:05 AM
> To: Alexei Starovoitov <alexei.starovoitov at gmail.com>
> Cc: James Morris <jamorris at linux.microsoft.com>; Anders Roxell
> <anders.roxell at linaro.org>; Alexei Starovoitov <ast at kernel.org>; Daniel
> Borkmann <daniel at iogearbox.net>; LKML <linux-kernel at vger.kernel.org>;
> Network Development <netdev at vger.kernel.org>; bpf
> <bpf at vger.kernel.org>
> Subject: Re: [PATCH] security: fix the default value of secid_to_secctx hook

I would *really* appreciate it if discussions about the LSM infrastructure
where done on the linux-security-module mail list. (added to CC).

> 
> On Sat, May 16, 2020 at 1:29 AM Alexei Starovoitov
> <alexei.starovoitov at gmail.com> wrote:
> >
> > On Thu, May 14, 2020 at 12:47 PM Alexei Starovoitov
> > <alexei.starovoitov at gmail.com> wrote:
> > >
> > > On Thu, May 14, 2020 at 12:43 PM James Morris
> > > <jamorris at linux.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