linux-kernel - [PATCH bpf-next] bpf/selftests: Use parent instead of last

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Date:   Mon, 12 Dec 2022 17:53:44 -0600
From:   David Vernet <void@...ifault.com>
To:     bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...a.com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, linux-kernel@...r.kernel.org,
        kernel-team@...a.com, kernel test robot <lkp@...el.com>
Subject: [PATCH bpf-next] bpf/selftests: Use parent instead of last_wakee in task kfunc test

Commit fe147956fca4 ("bpf/selftests: Add selftests for new task kfuncs")
added a negative selftest called task_kfunc_acquire_trusted_walked which
ensures that a BPF program that gets a struct task_struct * pointer from
walking a struct is properly rejected by the verifier if it tries to
pass that pointer to a task kfunc. In order to do this, it uses
task->last_wakee, but unfortunately that's not defined on UP builds.
Just use task->parent instead.

Reported-by: kernel test robot <lkp@...el.com>
Fixes: fe147956fca4 ("bpf/selftests: Add selftests for new task kfuncs")
Signed-off-by: David Vernet <void@...ifault.com>
---
 tools/testing/selftests/bpf/progs/task_kfunc_failure.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
index 87fa1db9d9b5..60508c20041f 100644
--- a/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
+++ b/tools/testing/selftests/bpf/progs/task_kfunc_failure.c
@@ -73,7 +73,7 @@ int BPF_PROG(task_kfunc_acquire_trusted_walked, struct task_struct *task, u64 cl
 	struct task_struct *acquired;
 
 	/* Can't invoke bpf_task_acquire() on a trusted pointer obtained from walking a struct. */
-	acquired = bpf_task_acquire(task->last_wakee);
+	acquired = bpf_task_acquire(task->parent);
 	bpf_task_release(acquired);
 
 	return 0;
-- 
2.38.1