linux-kernel - Re: [PATCH] dma-buf/sw_sync: Decrement refcount on error in sw_sync_ioctl_get

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Message-ID: <0e832ed8-9692-43ba-869d-8db3b419f3a9@amd.com>
Date: Mon, 31 Mar 2025 14:02:44 +0200
From: Christian König <christian.koenig@....com>
To: Dan Carpenter <dan.carpenter@...aro.org>,
 Rob Clark <robdclark@...omium.org>
Cc: Sumit Semwal <sumit.semwal@...aro.org>,
 Gustavo Padovan <gustavo@...ovan.org>, Dmitry Baryshkov <lumag@...nel.org>,
 Pekka Paalanen <pekka.paalanen@...labora.com>, linux-media@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
 linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] dma-buf/sw_sync: Decrement refcount on error in
 sw_sync_ioctl_get_deadline()

Am 31.03.25 um 11:45 schrieb Dan Carpenter:
> Call dma_fence_put(fence) before returning an error on this error path.
>
> Fixes: 70e67aaec2f4 ("dma-buf/sw_sync: Add fence deadline support")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>  drivers/dma-buf/sw_sync.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
> index f5905d67dedb..b7615c5c6cac 100644
> --- a/drivers/dma-buf/sw_sync.c
> +++ b/drivers/dma-buf/sw_sync.c
> @@ -438,8 +438,10 @@ static int sw_sync_ioctl_get_deadline(struct sync_timeline *obj, unsigned long a
>  		return -EINVAL;
>  
>  	pt = dma_fence_to_sync_pt(fence);
> -	if (!pt)
> +	if (!pt) {
> +		dma_fence_put(fence);
>  		return -EINVAL;
> +	}

Good catch.

I think it would be cleaner if we add an error label and then use "ret = -EINVAL; goto error;" here as well as a few lines below when ret is set to -ENOENT.

This way we can also avoid the ret = 0 in the declaration and let the compiler actually check the lifetime of the assignment.

Regards,
Christian.

>  
>  	spin_lock_irqsave(fence->lock, flags);
>  	if (test_bit(SW_SYNC_HAS_DEADLINE_BIT, &fence->flags)) {