linux-kernel - Should the return value of the rlookup_amd

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Message-ID: <ZuJxQKseMZjTjqdt@iZbp1asjb3cy8ks0srf007Z>
Date: Thu, 12 Sep 2024 12:42:40 +0800
From: Qianqiang Liu <qianqiang.liu@....com>
To: suravee.suthikulpanit@....com, will@...nel.org
Cc: vasant.hegde@....com, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Should the return value of the rlookup_amd_iommu be checked?

Hi,

I reviewed the following code:

1592 void amd_iommu_update_and_flush_device_table(struct protection_domain *domain)
1593 {
1594 	struct iommu_dev_data *dev_data;
1595 
1596 	list_for_each_entry(dev_data, &domain->dev_list, list) {
1597 		struct amd_iommu *iommu = rlookup_amd_iommu(dev_data->dev); <-
1598 
1599 		set_dte_entry(iommu, dev_data); <-
1600 		clone_aliases(iommu, dev_data->dev);
1601 	}
1602 
1603 	list_for_each_entry(dev_data, &domain->dev_list, list)
1604 		device_flush_dte(dev_data);
1605 
1606 	domain_flush_complete(domain);
1607 }

The "rlookup_amd_iommu" function may return NULL, and the "set_dte_entry" function
will call "get_dev_table" which will dereference the NULL pointer.

Is this an issue that may cause panic? Or will "rlookup_amd_iommu" function never
return NULL?

-- 
Best,
Qianqiang Liu