Re: [PATCH bpf v2 09/15] selftests/bpf: Fix double thread join in uprobe_multi_test

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 2/17/26 4:30 PM, Ihor Solodrai wrote:
> ASAN reported a "joining already joined thread" error. The
> release_child() may be called multiple times for the same struct
> child.
> 
> Fix with a memset(0) call at the end of release_child().
> 
> Acked-by: Mykyta Yatsenko <yatsenko@meta.com>
> Acked-by: Jiri Olsa <jolsa@kernel.org>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
> ---
>  tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> index 2ee17ef1dae2..be6ff1d4a75b 100644
> --- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> +++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
> @@ -68,6 +68,7 @@ static void release_child(struct child *child)
>  	close(child->c2p[1]);
>  	if (child->pid > 0)
>  		waitpid(child->pid, &child_status, 0);
> +	memset(child, 0, sizeof(*child));

The CI is failing because of this change.

Apparently, there are asserts on child object after it's released in
kick_child(), so we can't just memset it (without changing the test
logic).  The previous version of the fix [1], resetting only
child->thread, is more appropriate I think.

I missed this because uprobe_multi is in DENYLIST.asan

I'll wait a bit in case there is more feedback and send a v3.

[1] https://lore.kernel.org/bpf/20260212011356.3266753-10-ihor.solodrai@linux.dev/

>  }
>  
>  static void kick_child(struct child *child)