linux-kernel - [PATCH v10 3/4] iommu: Take lock before reading iommu group default domain type

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 24 Nov 2020 21:06:03 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Will Deacon <will@...nel.org>, Joerg Roedel <joro@...tes.org>
Cc:     Ashok Raj <ashok.raj@...el.com>, Christoph Hellwig <hch@....de>,
        Sohil Mehta <sohil.mehta@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>,
        Will Deacon <will.deacon@....com>,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH v10 3/4] iommu: Take lock before reading iommu group default domain type

From: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.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@....de>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Ashok Raj <ashok.raj@...el.com>
Cc: Will Deacon <will.deacon@....com>
Cc: Sohil Mehta <sohil.mehta@...el.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Signed-off-by: Lu Baolu <baolu.lu@...ux.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 5243b358b4b8..b4f69fb5e62b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -503,6 +503,7 @@ 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:
@@ -519,6 +520,7 @@ static ssize_t iommu_group_show_type(struct iommu_group *group,
 			break;
 		}
 	}
+	mutex_unlock(&group->mutex);
 	strcpy(buf, type);
 
 	return strlen(type);
-- 
2.25.1