linux-kernel - Re: [PATCH 2/3] drm/nouveau: Remove surplus if-branch

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <7603cbad-2fed-47cc-91f1-81d6f529afb8@amd.com>
Date: Thu, 10 Apr 2025 14:15:49 +0200
From: Christian König <christian.koenig@....com>
To: Philipp Stanner <phasta@...nel.org>, Lyude Paul <lyude@...hat.com>,
 Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Sabrina Dubroca <sd@...asysnail.net>,
 Sumit Semwal <sumit.semwal@...aro.org>
Cc: dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH 2/3] drm/nouveau: Remove surplus if-branch

Am 10.04.25 um 11:24 schrieb Philipp Stanner:
> nouveau_fence_done() contains an if-branch which checks for the
> existence of either of two fence backend ops. Those two are the only
> backend ops existing in Nouveau, however; and at least one backend ops
> must be in use for the entire driver to be able to work. The if branch
> is, therefore, surplus.
>
> Remove the if-branch.

What happens here is that nouveau checks if the fence comes from itself or some external source.

So when you remove that check you potentially illegally uses nouveau_fctx() on a non-nouveau fence.

Regards,
Christian.

>
> Signed-off-by: Philipp Stanner <phasta@...nel.org>
> ---
>  drivers/gpu/drm/nouveau/nouveau_fence.c | 24 +++++++++++-------------
>  1 file changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c
> index 33535987d8ed..db6f4494405c 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
> @@ -259,21 +259,19 @@ nouveau_fence_emit(struct nouveau_fence *fence)
>  bool
>  nouveau_fence_done(struct nouveau_fence *fence)
>  {
> -	if (fence->base.ops == &nouveau_fence_ops_legacy ||
> -	    fence->base.ops == &nouveau_fence_ops_uevent) {
> -		struct nouveau_fence_chan *fctx = nouveau_fctx(fence);
> -		struct nouveau_channel *chan;
> -		unsigned long flags;
> +	struct nouveau_fence_chan *fctx = nouveau_fctx(fence);
> +	struct nouveau_channel *chan;
> +	unsigned long flags;
>  
> -		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->base.flags))
> -			return true;
> +	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->base.flags))
> +		return true;
> +
> +	spin_lock_irqsave(&fctx->lock, flags);
> +	chan = rcu_dereference_protected(fence->channel, lockdep_is_held(&fctx->lock));
> +	if (chan && nouveau_fence_update(chan, fctx))
> +		nvif_event_block(&fctx->event);
> +	spin_unlock_irqrestore(&fctx->lock, flags);
>  
> -		spin_lock_irqsave(&fctx->lock, flags);
> -		chan = rcu_dereference_protected(fence->channel, lockdep_is_held(&fctx->lock));
> -		if (chan && nouveau_fence_update(chan, fctx))
> -			nvif_event_block(&fctx->event);
> -		spin_unlock_irqrestore(&fctx->lock, flags);
> -	}
>  	return test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->base.flags);
>  }
>