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@efficios.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 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).
-- 
2.39.5

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@efficios.com>
> Cc: Peter Zijlstra (Intel) <peterz@infradead.org>

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@gmail.com/


> ---
>   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

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     40724ecafccb1fb62b66264854e8c3ad394c8f3d
Gitweb:        https://git.kernel.org/tip/40724ecafccb1fb62b66264854e8c3ad394c8f3d
Author:        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
AuthorDate:    Thu, 16 Jan 2025 15:59:56 -05:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 21 Jan 2025 08:10:51 +01:00

rseq: Fix rseq unregistration regression

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@efficios.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250116205956.836074-1-mathieu.desnoyers@efficios.com
---
 kernel/rseq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rseq.c b/kernel/rseq.c
index e04bb30..442aba2 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).