linux-kernel - [PATCH 4.19 169/321] vfio/spapr_tce: Get rid of possible infinite loop

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Message-Id: <20191203223435.927454925@linuxfoundation.org>
Date:   Tue,  3 Dec 2019 23:33:55 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Alexey Kardashevskiy <aik@...abs.ru>,
        David Gibson <david@...son.dropbear.id.au>,
        Alex Williamson <alex.williamson@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 169/321] vfio/spapr_tce: Get rid of possible infinite loop

From: Alexey Kardashevskiy <aik@...abs.ru>

[ Upstream commit 517ad4ae8aa93dccdb9a88c27257ecb421c9e848 ]

As a part of cleanup, the SPAPR TCE IOMMU subdriver releases preregistered
memory. If there is a bug in memory release, the loop in
tce_iommu_release() becomes infinite; this actually happened to me.

This makes the loop finite and prints a warning on every failure to make
the code more bug prone.

Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
Reviewed-by: David Gibson <david@...son.dropbear.id.au>
Acked-by: Alex Williamson <alex.williamson@...hat.com>
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/vfio/vfio_iommu_spapr_tce.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 96721b154454f..ec53310f16136 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -371,6 +371,7 @@ static void tce_iommu_release(void *iommu_data)
 {
 	struct tce_container *container = iommu_data;
 	struct tce_iommu_group *tcegrp;
+	struct tce_iommu_prereg *tcemem, *tmtmp;
 	long i;
 
 	while (tce_groups_attached(container)) {
@@ -393,13 +394,8 @@ static void tce_iommu_release(void *iommu_data)
 		tce_iommu_free_table(container, tbl);
 	}
 
-	while (!list_empty(&container->prereg_list)) {
-		struct tce_iommu_prereg *tcemem;
-
-		tcemem = list_first_entry(&container->prereg_list,
-				struct tce_iommu_prereg, next);
-		WARN_ON_ONCE(tce_iommu_prereg_free(container, tcemem));
-	}
+	list_for_each_entry_safe(tcemem, tmtmp, &container->prereg_list, next)
+		WARN_ON(tce_iommu_prereg_free(container, tcemem));
 
 	tce_iommu_disable(container);
 	if (container->mm)
-- 
2.20.1