linux-kernel - Re: [PATCH] iommu: apple-dart: fix potential null pointer deref

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Message-ID: <Z9TBEAJkOrHIWype@blossom>
Date: Fri, 14 Mar 2025 19:51:44 -0400
From: Alyssa Rosenzweig <alyssa@...enzweig.io>
To: Qasim Ijaz <qasdev00@...il.com>
Cc: marcan@...can.st, fnkl.kernel@...il.com,
	Sven Peter <sven@...npeter.dev>, Janne Grunau <j@...nau.net>,
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>, asahi@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu: apple-dart: fix potential null pointer deref

Reviewed-by: Alyssa Rosenzweig <alyssa@...enzweig.io>

Le Fri , Mar 14, 2025 at 11:01:02PM +0000, Qasim Ijaz a écrit :
> If kzalloc() fails, accessing cfg->supports_bypass causes a null pointer dereference. 
> 
> Fix by checking for NULL immediately after allocation and returning -ENOMEM.
> 
> Fixes: 3bc0102835f6 ("iommu: apple-dart: Allow mismatched bypass support")
> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
> ---
>  drivers/iommu/apple-dart.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> index 13ccb801f52a..e13501541fdd 100644
> --- a/drivers/iommu/apple-dart.c
> +++ b/drivers/iommu/apple-dart.c
> @@ -797,12 +797,11 @@ static int apple_dart_of_xlate(struct device *dev,
>  
>  	if (!cfg) {
>  		cfg = kzalloc(sizeof(*cfg), GFP_KERNEL);
> -
> +		if (!cfg)
> +			return -ENOMEM;
>  		/* Will be ANDed with DART capabilities */
>  		cfg->supports_bypass = true;
>  	}
> -	if (!cfg)
> -		return -ENOMEM;
>  	dev_iommu_priv_set(dev, cfg);
>  
>  	cfg_dart = cfg->stream_maps[0].dart;
> -- 
> 2.39.5
>