linux-kernel - [PATCH] iommu/vt-d: Fix an unbalanced rcu_read_lock/rcu_read

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Message-Id: <40cc077ca5f543614eab2a10e84d29dd190273f6.1636217517.git.christophe.jaillet@wanadoo.fr>
Date:   Sat,  6 Nov 2021 17:53:18 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     dwmw2@...radead.org, baolu.lu@...ux.intel.com, joro@...tes.org,
        will@...nel.org, kevin.tian@...el.com
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: [PATCH] iommu/vt-d: Fix an unbalanced rcu_read_lock/rcu_read_unlock()

If we return -EOPNOTSUPP, the rcu lock remains lock. This is spurious.
Go through the end of the function instead. This way, the missing
'rcu_read_unlock()' is called.

Fixes: 7afd7f6aa21a ("iommu/vt-d: Check FL and SL capability sanity in scalable mode")
Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
This patch is speculative, review with care.
---
 drivers/iommu/intel/cap_audit.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/intel/cap_audit.c b/drivers/iommu/intel/cap_audit.c
index b39d223926a4..71596fc62822 100644
--- a/drivers/iommu/intel/cap_audit.c
+++ b/drivers/iommu/intel/cap_audit.c
@@ -144,6 +144,7 @@ static int cap_audit_static(struct intel_iommu *iommu, enum cap_audit_type type)
 {
 	struct dmar_drhd_unit *d;
 	struct intel_iommu *i;
+	int rc = 0;
 
 	rcu_read_lock();
 	if (list_empty(&dmar_drhd_units))
@@ -169,11 +170,11 @@ static int cap_audit_static(struct intel_iommu *iommu, enum cap_audit_type type)
 	 */
 	if (intel_cap_smts_sanity() &&
 	    !intel_cap_flts_sanity() && !intel_cap_slts_sanity())
-		return -EOPNOTSUPP;
+		rc = -EOPNOTSUPP;
 
 out:
 	rcu_read_unlock();
-	return 0;
+	return rc;
 }
 
 int intel_cap_audit(enum cap_audit_type type, struct intel_iommu *iommu)
-- 
2.30.2