Compatible vdso's size is bigger than reserved buf

[Radim Vansa]

Hello Martin,

thanks for bringing this to our attention. It looks like upstream CRIU 
has it already patched to 4 pages [1], but we haven't cherry-picked that 
change yet. Regarding VDSO, we shall also cherry-pick the fixes for 
kernel 6.13+ which introduces the [vvar_clock] VMA [2][3].

Could you send a PR with the cherry pick to https://github.com/crac/criu ?

Thanks!

Radim

[1] 
https://github.com/checkpoint-restore/criu/commit/70a9cd6fbf46d96b7bd49f38f3e013bd892a990e
[2] 
https://github.com/checkpoint-restore/criu/commit/058572e91dea1d8ac9c345e69e08a58e8abfacbb
[3] 
https://github.com/checkpoint-restore/criu/commit/720bf67e065525133f4b0209baa7142192fbb667

On 23. 05. 25 13:26, Martin Welgemoed wrote:
> Caution: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
>
>
> Hello everyone,
>
> CRaC has been working quite well for us. Recently we upgraded
> Kubernetes in GKE to 1.31 (kernel 6.6.72+) and since then CRaC
> snapshots fail to restore with "Error: Compatible vdso's size is
> bigger than reserved buf".
>
> This is specifically for the 32bit compat VDSO. Running strace
> confirms that the kernel now has it at 3 pages (12kb) in size.
>
> arch_prctl(ARCH_MAP_VDSO_32, 0x7ffd1d983000) = 12288
>
> In COMPAT_VDSO_BUF_SZ CRaC only allocates 2 pages for it
> https://github.com/CRaC/criu/blob/e7aefe4f9e499597ddf484394d29fc4752b674dd/criu/vdso.c#L482
>
> I'm somewhat surprised by it being 3 pages, because on my own local
> machine (6.14.5-arch1-1) it is still 8kb:
>
> arch_prctl(ARCH_MAP_VDSO_32, 0x789ea0a00000) = 8192
>
> I think this is possibly a GKE configuration thing for its kernel build.
>
> Does anyone else have experience with this or a solution for it? I
> think increasing the COMPAT_VDSO_BUF_SZ could solve it but I am not
> experienced enough with CRIU or the VDSO to fully judge the
> implications of this.
>
> Kind regards,
>
> --
> Martin Welgemoed
> Scala Engineer
>
> martin.welgemoed at commercetools.com
> T. +49 (89) 99 82 996-0
> commercetools B.V. | Prins Bernhardplein 200 | 1097 JB Amsterdam
>
> --
>
>
>
>
>
> commercetools B.V.
> Prins Bernhardplein 200, 1097 JB Amsterdam |
> Netherlands
> www.commercetools.com <http://www.commercetools.com/>
>
>
> --
>
>
>
>
>
> commercetools GmbH
> Adams-Lehmann-Str. 44 | 80797 Munich | Germany
> Register: HRB 161496 | Local Court at Munich
> Managing Directors Dirk Hörig
> | Denis Werner
>
>
> <https://elevate.commercetools.com//?utm_source=Email&utm_medium=Outreach&utm_content=Elevate-2025&utm_campaign=events-global>