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

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Message-Id: <20250314230102.11008-1-qasdev00@gmail.com>
Date: Fri, 14 Mar 2025 23:01:02 +0000
From: Qasim Ijaz <qasdev00@...il.com>
To: marcan@...can.st,
	fnkl.kernel@...il.com,
	Sven Peter <sven@...npeter.dev>,
	Janne Grunau <j@...nau.net>,
	Alyssa Rosenzweig <alyssa@...enzweig.io>,
	Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>
Cc: asahi@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] iommu: apple-dart: fix potential null pointer deref

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