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From: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
To: iommu@lists.linux-foundation.org
Cc: Ashok Raj <ashok.raj@intel.com>,
	Will Deacon <will.deacon@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Christoph Hellwig <hch@lst.de>
Subject: [PATCH V4 2/3] iommu: Take lock before reading iommu group default domain type
Date: Thu,  4 Jun 2020 18:32:07 -0700	[thread overview]
Message-ID: <379b0d7307bb76699e2438a21f6c8259a7538ef7.1591290586.git.sai.praneeth.prakhya@intel.com> (raw)
In-Reply-To: <cover.1591290586.git.sai.praneeth.prakhya@intel.com>

"/sys/kernel/iommu_groups/<grp_id>/type" file could be read to find out the
default domain type of an iommu group. The default domain of an iommu group
doesn't change after booting and hence could be read directly. But,
after addding support to dynamically change iommu group default domain, the
above assumption no longer stays valid.

iommu group default domain type could be changed at any time by writing to
"/sys/kernel/iommu_groups/<grp_id>/type". So, take group mutex before
reading iommu group default domain type so that the user wouldn't see stale
values or iommu_group_show_type() doesn't try to derefernce stale pointers.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Sohil Mehta <sohil.mehta@intel.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
---
 drivers/iommu/iommu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index b023f06f12d6..eb133ee5c13a 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -501,6 +501,7 @@ static ssize_t iommu_group_show_type(struct iommu_group *group,
 {
 	char *type = "unknown\n";
 
+	mutex_lock(&group->mutex);
 	if (group->default_domain) {
 		switch (group->default_domain->type) {
 		case IOMMU_DOMAIN_BLOCKED:
@@ -517,6 +518,7 @@ static ssize_t iommu_group_show_type(struct iommu_group *group,
 			break;
 		}
 	}
+	mutex_unlock(&group->mutex);
 	strcpy(buf, type);
 
 	return strlen(type);
-- 
2.19.1

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  parent reply	other threads:[~2020-06-05  1:35 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-05  1:32 [PATCH V4 0/3] iommu: Add support to change default domain of an iommu group Sai Praneeth Prakhya
2020-06-05  1:32 ` [PATCH V4 1/3] " Sai Praneeth Prakhya
2020-06-08  1:49   ` Lu Baolu
2020-06-30  9:16   ` Joerg Roedel
2020-07-01  3:04     ` Prakhya, Sai Praneeth
2020-07-14 18:23       ` Prakhya, Sai Praneeth
2020-07-22 13:52         ` Joerg Roedel
2020-07-22 17:14           ` Prakhya, Sai Praneeth
2020-06-05  1:32 ` Sai Praneeth Prakhya [this message]
2020-06-08  1:50   ` [PATCH V4 2/3] iommu: Take lock before reading iommu group default domain type Lu Baolu
2020-06-05  1:32 ` [PATCH V4 3/3] iommu: Document usage of "/sys/kernel/iommu_groups/<grp_id>/type" file Sai Praneeth Prakhya
2020-06-08  1:50   ` Lu Baolu
2020-06-26 21:34 ` [PATCH V4 0/3] iommu: Add support to change default domain of an iommu group Prakhya, Sai Praneeth

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