[libvirt] [PATCH 6/6] security_selinux: Play nicely with network FS that only emulates SELinux

[Martin Kletzander]

On Thu, Aug 22, 2019 at 05:19:09PM +0200, Michal Privoznik wrote:
>There are some network file systems that do support XATTRs (e.g.
>gluster via FUSE). And they appear to support SELinux too.
>However, not really. Problem is, that it is impossible to change
>SELinux label of a file stored there, and yet we claim success
>(rightfully - hypervisor succeeds in opening the file). But this
>creates a problem for us - from XATTR bookkeeping POV, we haven't
>changed the label and thus if we remembered any label, we must
>roll back and remove it.
>
>Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1740506
>
>Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>---
> src/security/security_selinux.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
>diff --git a/src/security/security_selinux.c b/src/security/security_selinux.c
>index 855eaafdda..4d0c7a46ae 100644
>--- a/src/security/security_selinux.c
>+++ b/src/security/security_selinux.c
>@@ -1384,12 +1384,22 @@ virSecuritySELinuxSetFilecon(virSecurityManagerPtr mgr,
>         }
>     }
>
>-    if (virSecuritySELinuxSetFileconImpl(path, tcon, privileged) < 0)
>+    if ((rc = virSecuritySELinuxSetFileconImpl(path, tcon, privileged)) < 0)

I wonder why so many people try to stuff as much as possible into the condition
instead of doing:

    rc = func();
    if (rc < 0)

But anyway, this is not related to this commit, just a place to rent.

>         goto cleanup;
>
>+    /* At this point, we can claim success. However,
>+     * virSecuritySELinuxSetFileconImpl() could returned 0
>+     * (SELinux label changed) or 1 (SELinux label NOT changed in
>+     * a non-critical fashion). If the label was NOT changed, we
>+     * must remove remembered label then - there's nothing to
>+     * remember, is there? But of the label was changed, don't

s/of/if/, but I think it is overcomplicated.  Why don't you just:

    /* Do not try restoring the label if it was not changed
     * (setting it failed in a non-critical fashion) */

Either way:

Reviewed-by: Martin Kletzander <mkletzan at redhat.com>
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