linux-kernel - [PATCH 2/5] iommu/amd: Do not loop forever when trying to increase address space

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Message-Id: <20200504125413.16798-3-joro@8bytes.org>
Date:   Mon,  4 May 2020 14:54:10 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     iommu@...ts.linux-foundation.org
Cc:     Qian Cai <cai@....pw>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org, Joerg Roedel <jroedel@...e.de>
Subject: [PATCH 2/5] iommu/amd: Do not loop forever when trying to increase address space

From: Joerg Roedel <jroedel@...e.de>

When increase_address_space() fails to allocate memory, alloc_pte()
will call it again until it succeeds. Do not loop forever while trying
to increase the address space and just return an error instead.

Tested-by: Qian Cai <cai@....pw>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/amd_iommu.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 28229a38af4d..68da484a69dd 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1489,8 +1489,19 @@ static u64 *alloc_pte(struct protection_domain *domain,
 	amd_iommu_domain_get_pgtable(domain, &pgtable);
 
 	while (address > PM_LEVEL_SIZE(pgtable.mode)) {
-		*updated = increase_address_space(domain, address, gfp) || *updated;
+		bool upd = increase_address_space(domain, address, gfp);
+
+		/* Read new values to check if update was successful */
 		amd_iommu_domain_get_pgtable(domain, &pgtable);
+
+		/*
+		 * Return an error if there is no memory to update the
+		 * page-table.
+		 */
+		if (!upd && (address > PM_LEVEL_SIZE(pgtable.mode)))
+			return NULL;
+
+		*updated = *updated || upd;
 	}
 
 
-- 
2.17.1