Re: [PATCH for sched/core] rseq: Fix rseq unregistration

[Mathieu Desnoyers]

On 2025-01-16 15:59, Mathieu Desnoyers wrote:
> A logic inversion in rseq_reset_rseq_cpu_node_id() causes the rseq
> unregistration to fail when rseq_validate_ro_fields() succeeds rather
> than the opposite.
>
> This affects both CONFIG_DEBUG_RSEQ=y and CONFIG_DEBUG_RSEQ=n.
>
> Fixes: 7d5265ffcd8b ("rseq: Validate read-only fields under DEBUG_RSEQ config")
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

Ingo, Peter, this fix should have been part of the PR sent to Linus
earlier today [1]. Otherwise rseq unregistration is broken.

Thanks,

Mathieu

[1] https://lore.kernel.org/lkml/Z44ufdYZWaM50kxF@xxxxxxxxx/


> ---
>   kernel/rseq.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> 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).

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com