[PATCH v16 6/8] nptl: Move the rseq area to the 'extra TLS' block

[Michael Jeanson]

On 2025-01-16 12:04, Michael Jeanson wrote:
>> I'll have a look at linux-next and check if I can reprod on another
>> architecture.

So the issue is indeed specific to linux-next and affects all architectures,
the offending commit is :

 7d5265ffcd8b (rseq: Validate read-only fields under DEBUG_RSEQ config)

It's a simple logic inversion bug that breaks unregistration, Mathieu has
already sent an updated patch. In the mean time, you can apply this to
your kernel sources:

diff --git a/kernel/rseq.c b/kernel/rseq.c
index e04bb30a2eb8..442aba29bc4c 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -201,7 +201,7 @@ static int rseq_reset_rseq_cpu_node_id(struct task_struct *t)
 	/*
 	 * Validate read-only rseq fields.
 	 */
-	if (!rseq_validate_ro_fields(t))
+	if (rseq_validate_ro_fields(t))
 		return -EFAULT;
 	/*
 	 * Reset cpu_id_start to its initial state (0).