Re: [PATCH v3] libsemanage: Fall back to semanage_copy_dir when rename() fails

[Petr Lautrbach <plautrba@redhat.com>]

Ondrej Mosnacek <omosnace@redhat.com> writes:

> On Thu, Mar 24, 2022 at 1:01 PM Petr Lautrbach <plautrba@redhat.com> wrote:
>> In some circumstances, like semanage-store being on overlayfs, rename()
>> could fail with EXDEV - Invalid cross-device link. This is due to the
>> fact that overlays doesn't support rename() if source and target are not
>> on the same layer, e.g. in containers built from several layers. Even
>> though it's not atomic operation, it's better to try to copy files from
>> src to dst on our own in this case. Next rebuild will probably not fail
>> as the new directories will be on the same layer.
>>
>> Fixes: https://github.com/SELinuxProject/selinux/issues/343
>>
>> Reproducer:
>>
>>     $ cd selinux1
>>
>>     $ cat Dockerfile
>>     FROM fedora:35
>>     RUN dnf install -y selinux-policy selinux-policy-targeted
>>
>>     $ podman build -t localhost/selinux . --no-cache
>>
>>     $ cd ../selinux2
>>
>>     $ cat Dockerfile
>>     FROM localhost/selinux
>>     RUN semodule -B
>>
>>     $ podman build -t localhost/selinux2 . --no-cache
>>     STEP 2/2: RUN semodule -B
>>     libsemanage.semanage_commit_sandbox: Error while renaming /var/lib/selinux/targeted/active to /var/lib/selinux/targeted/previous. (Invalid cross-device link).
>>     semodule:  Failed!
>>     Error: error building at STEP "RUN semodule -B": error while running runtime: exit status 1
>>
>> With the fix:
>>
>>     $ podman build -t localhost/selinux2 . --no-cache
>>     STEP 2/2: RUN semodule -B
>>     libsemanage.semanage_rename: Warning: rename(/var/lib/selinux/targeted/active, /var/lib/selinux/targeted/previous) failed: Invalid cross-device link, fall back to non-atomic semanage_copy_dir_flags()
>>
>>     COMMIT localhost/selinux2
>>     --> d2cfcebc1a1
>>     Successfully tagged localhost/selinux2:latest
>>     d2cfcebc1a1b34f1c2cd661ac18292b0612c3e5fa71d6fa1441be244da91b1af
>>
>> Reported-by: Joseph Marrero Corchado <jmarrero@redhat.com>
>> Signed-off-by: Petr Lautrbach <plautrba@redhat.com>
>> ---
>>
>> v2
>> - improve the commit message
>> - use WARN() instead of fprintf(stderr,
>>
>> v3
>> - WARN without \n at the end
>> - split long line
>
> Acked-by: Ondrej Mosnacek <omosnace@redhat.com>
>
> Note that I didn't give the logic a thorough review, so I'd prefer
> someone else to give it a final look and merge it.

Merged.



> -- 
> Ondrej Mosnacek
> Software Engineer, Linux Security - SELinux kernel
> Red Hat, Inc.