[PATCH] security: fix the logic in security_inode_getsecctx()

[Stephen Smalley]

On Fri, Jan 26, 2024 at 5:44 AM Ondrej Mosnacek <omosnace at redhat.com> wrote:
>
> The inode_getsecctx LSM hook has previously been corrected to have
> -EOPNOTSUPP instead of 0 as the default return value to fix BPF LSM
> behavior. However, the call_int_hook()-generated loop in
> security_inode_getsecctx() was left treating 0 as the neutral value, so
> after an LSM returns 0, the loop continues to try other LSMs, and if one
> of them returns a non-zero value, the function immediately returns with
> said value. So in a situation where SELinux and the BPF LSMs registered
> this hook, -EOPNOTSUPP would be incorrectly returned whenever SELinux
> returned 0.
>
> Fix this by open-coding the call_int_hook() loop and making it use the
> correct LSM_RET_DEFAULT() value as the neutral one, similar to what
> other hooks do.
>
> Reported-by: Stephen Smalley <stephen.smalley.work at gmail.com>
> Link: https://lore.kernel.org/selinux/CAEjxPJ4ev-pasUwGx48fDhnmjBnq_Wh90jYPwRQRAqXxmOKD4Q@mail.gmail.com/
> Fixes: b36995b8609a ("lsm: fix default return value for inode_getsecctx")
> Signed-off-by: Ondrej Mosnacek <omosnace at redhat.com>
> ---
>
> I ran 'tools/nfs.sh' on the patch and even though it fixes the most
> serious issue that Stephen reported, some of the tests are still
> failing under NFS (but I will presume that these are pre-existing issues
> not caused by the patch).

Do you have a list of the failing tests? For me, it was hanging on
unix_socket and thus not getting to many of the tests. I would like to
triage the still-failing ones to confirm that they are in fact
known/expected failures for NFS.