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From: Simon Chopin <simon.chopin@canonical.com>
To: Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>
Cc: GNU C Library <libc-alpha@sourceware.org>,
	Xi Ruoyao <xry111@xry111.site>
Subject: Re: [PATCH v2] tests: gracefully handle AppArmor userns containment
Date: Fri, 16 Feb 2024 15:57:20 +0000	[thread overview]
Message-ID: <CAOOWow1vz=aJ7Jd+_Ry=JMhPYBoSgnYNhK-OW1N_pbnJv57yzw@mail.gmail.com> (raw)
In-Reply-To: <CB9608D8-73AF-4A6F-B07D-B604378E8B5C@linaro.org>

Hi Maxim,

On mar. 13 févr. 2024 11:36:34, Maxim Kuvyrkov wrote:
> > On Feb 6, 2024, at 14:59, Simon Chopin <simon.chopin@canonical.com> wrote:
> >
> > Recent AppArmor containment allows restricting unprivileged user
> > namespaces, which is enabled by default on recent Ubuntu systems.
> >
> > When that happens, the affected tests will now be considered unsupported
> > rather than simply failing.
> >
> > Further information:
> >
> > * https://gitlab.com/apparmor/apparmor/-/wikis/unprivileged_userns_restriction
> > * https://ubuntu.com/blog/ubuntu-23-10-restricted-unprivileged-user-namespaces
> >
> > V2:
> > * Fix duplicated line in check_unshare_hints
> > * Also handle similar failure in tst-pidfd_getpid
>
> Looks good, with below comments addressed.
>
> Please CC reviewers of the previous versions of the patch -- Xi Ruoyao in this case.

ACK

>
> >
> > Signed-off-by: Simon Chopin <simon.chopin@canonical.com>
> > ---
> > support/test-container.c                   | 7 +++++--
> > sysdeps/unix/sysv/linux/tst-pidfd_getpid.c | 3 ++-
> > 2 files changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/support/test-container.c b/support/test-container.c
> > index adf2b30215..af66cece51 100644
> > --- a/support/test-container.c
> > +++ b/support/test-container.c
> > @@ -682,6 +682,8 @@ check_for_unshare_hints (int require_pidns)
> >     { "/proc/sys/kernel/unprivileged_userns_clone", 0, 1, 0 },
> >     /* ALT Linux has an alternate way of doing the same.  */
> >     { "/proc/sys/kernel/userns_restrict", 1, 0, 0 },
> > +    /* AppArmor can also disable unprivileged user namespaces */
>
> GNU coding style is to finish comment sentences with a dot, followed by two spaces.  E.g.,
> /* My new comment.  */

ACK

>
> > +    { "/proc/sys/kernel/apparmor_restrict_unprivileged_userns", 1, 0, 0 },
> >     /* Linux kernel >= 4.9 has a configurable limit on the number of
> >        each namespace.  Some distros set the limit to zero to disable the
> >        corresponding namespace as a "security policy".  */
> > @@ -1108,10 +1110,11 @@ main (int argc, char **argv)
> >     {
> >       /* Older kernels may not support all the options, or security
> > policy may block this call.  */
> > -      if (errno == EINVAL || errno == EPERM || errno == ENOSPC)
> > +      if (errno == EINVAL || errno == EPERM
> > +          || errno == ENOSPC || errno == EACCES)
>
> Where is EACCES coming from?  I could not find documentation mentioning EACCES as a possible error condition for unshare().

This is injected by AppArmor when it prevents a syscall. According to
coworkers it's a fairly standard value for LSM modules, and some cursory
code source sleuthing goes in that sense, but the only instance of
actual documentation that mentions this is a mention in passing in
https://manpages.ubuntu.com/manpages/jammy/man5/apparmor.d.5.html

I'll add some more info about it in the commit log.

>
> > {
> >  int saved_errno = errno;
> > -  if (errno == EPERM || errno == ENOSPC)
> > +  if (errno == EPERM || errno == ENOSPC || errno == EACCES)
> >    check_for_unshare_hints (require_pidns);
> >  FAIL_UNSUPPORTED ("unable to unshare user/fs: %s", strerror (saved_errno));
> > }
> > diff --git a/sysdeps/unix/sysv/linux/tst-pidfd_getpid.c b/sysdeps/unix/sysv/linux/tst-pidfd_getpid.c
> > index 0354da5abb..ef62fbe941 100644
> > --- a/sysdeps/unix/sysv/linux/tst-pidfd_getpid.c
> > +++ b/sysdeps/unix/sysv/linux/tst-pidfd_getpid.c
> > @@ -61,7 +61,8 @@ do_test (void)
> >  {
> >    /* Older kernels may not support all the options, or security
> >       policy may block this call.  */
> > -    if (errno == EINVAL || errno == EPERM || errno == ENOSPC)
> > +    if (errno == EINVAL || errno == EPERM
> > +        || errno == ENOSPC || errno == EACCES)
> >      exit (EXIT_UNSUPPORTED);
> >    FAIL_EXIT1 ("unshare user/fs/pid failed: %m");
> >  }
> >
> > base-commit: fa3eb7d5e7d32ca1ad48b48a7eb6d15b8382c3a7
> > --
> > 2.40.1
> >
>
> Thanks,
>
> --
> Maxim Kuvyrkov
> https://www.linaro.org
>
>

      parent reply	other threads:[~2024-02-16 15:57 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-01 12:01 [PATCH] test-container: gracefully handle AppArmor containment Simon Chopin
2024-02-01 12:20 ` Xi Ruoyao
2024-02-06 11:01   ` Simon Chopin
2024-02-06 10:59 ` [PATCH v2] tests: gracefully handle AppArmor userns containment Simon Chopin
2024-02-13  7:36   ` Maxim Kuvyrkov
2024-02-14  7:53     ` Florian Weimer
2024-02-16 15:57     ` Simon Chopin [this message]

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