Re: [PATCH] gpu: host1x: Fix passing zero to ERR_PTR in host1x_iommu_attach()

[Mikko Perttunen <mperttunen@nvidia.com>]

On Monday, February 9, 2026 10:14 PM Alper Ak wrote:
> When iommu_attach_group() returns -ENODEV, the code sets err to 0 but
> still falls through to the error path, returning ERR_PTR(0).
> 
> Returning ERR_PTR(0) evaluates to NULL and breaks the ERR_PTR/IS_ERR
> contract, causing the error to be silently ignored and potentially
> leading to NULL pointer dereferences by callers.
> 
> Fix this by returning NULL when err is zero, and ERR_PTR(err) only
> for actual error codes.

This commit message doesn't make sense. First you say that the function has a bug because ERR_PTR(0) evaluates to NULL and can cause problems when callers don't handle NULL. Then you fix that by returning NULL explicitly.

While returning NULL through ERR_PTR(0) may not be very beautiful, this function is defined to return NULL in certain cases and so the behavior is correct.

Mikko

> 
> This issue was reported by the Smatch static analyzer.
> 
> Fixes: 06867a362de0 ("gpu: host1x: Set DMA mask based on IOMMU setup")
> Signed-off-by: Alper Ak <alperyasinak1@gmail.com>
> ---
>  drivers/gpu/host1x/dev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c
> index 3f475f0e6545..46a570b861ac 100644
> --- a/drivers/gpu/host1x/dev.c
> +++ b/drivers/gpu/host1x/dev.c
> @@ -450,7 +450,7 @@ static struct iommu_domain *host1x_iommu_attach(struct host1x *host)
>  	iommu_group_put(host->group);
>  	host->group = NULL;
>  
> -	return ERR_PTR(err);
> +	return err ? ERR_PTR(err) : NULL;
>  }
>  
>  static int host1x_iommu_init(struct host1x *host)
> -- 
> 2.43.0
> 
>