Re: [PATCH bpf] selftests/bpf: Look up unpinned maps by ID in bpftool_maps_access

["Alexis Lothoré" <alexis.lothore@bootlin.com>]

Hi Tianyi,

On Wed Nov 4, 2026 at 7:33 PM CET, Tianyi Chen wrote:
> The unpinned subtests pass "name prot_map" or "name not_prot_map" to
> bpftool. Both maps are used by programs attached through trampolines,
> which are freed only after RCU grace periods and hold their map
> references until then. A run's maps therefore stay in the map ID table
> after its skeleton is destroyed, for about 300 ms in an x86-64 VM.
>
> If the test runs again within that window, the name matches maps from
> both runs, bpftool fails with "several maps match this handle", and
> the unpinned subtests fail.
>
> Look up these maps by ID instead and drop the now unused map names.
>
> Fixes: 2d96bbdfd3b5 ("selftests/bpf: convert test_bpftool_map_access.sh into test_progs framework")
> Assisted-by: LLM
> Signed-off-by: Tianyi Chen <hi@tychen.cc>

I've reproduced locally in my VM the mentioned issue (and saw the
"Error: several maps match this handle") with:

  while true; do ./test_progs -a bpftool_maps_access/unprotected_unpinned; done

With your patch applied, I don't see the error anymore. The fix
looks sane to me.

Tested-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
Reviewed-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>

Thanks, Alexis

-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com