linux-kernel - [PATCH v2 4/5] iommu/arm-smmu-qcom: Consistently initialize stream mappings

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]

Message-Id: <20200717001619.325317-5-bjorn.andersson@linaro.org>
Date:   Thu, 16 Jul 2020 17:16:18 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jonathan Marek <jonathan@...ek.ca>,
        linux-arm-msm@...r.kernel.org,
        John Stultz <john.stultz@...aro.org>,
        Vinod Koul <vkoul@...nel.org>
Subject: [PATCH v2 4/5] iommu/arm-smmu-qcom: Consistently initialize stream mappings

Firmware that traps writes to S2CR to translate BYPASS into FAULT also
ignores writes of type FAULT. As such booting with "disable_bypass" set
will result in all S2CR registers left as configured by the bootloader.

This has been seen to result in indeterministic results, as these
mappings might linger and reference context banks that Linux is
reconfiguring.

Use the fact that BYPASS writes result in FAULT type to force all stream
mappings to FAULT.

Tested-by: John Stultz <john.stultz@...aro.org>
Tested-by: Vinod Koul <vkoul@...nel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
---

Changes since v1:
- Fixed subject spelling mistake
- Picked up tested-by

 drivers/iommu/arm-smmu-qcom.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
index d95a5ee8c83c..10eb024981d1 100644
--- a/drivers/iommu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm-smmu-qcom.c
@@ -27,6 +27,7 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
 {
 	unsigned int last_s2cr = ARM_SMMU_GR0_S2CR(smmu->num_mapping_groups - 1);
 	u32 reg;
+	int i;
 
 	/*
 	 * With some firmware writes to S2CR of type FAULT are ignored, and
@@ -37,9 +38,24 @@ static int qcom_smmu_cfg_probe(struct arm_smmu_device *smmu)
 					    FIELD_PREP(ARM_SMMU_S2CR_CBNDX, 0xff) |
 					    FIELD_PREP(ARM_SMMU_S2CR_PRIVCFG, S2CR_PRIVCFG_DEFAULT));
 	reg = arm_smmu_gr0_read(smmu, last_s2cr);
-	if (FIELD_GET(ARM_SMMU_S2CR_TYPE, reg) != S2CR_TYPE_BYPASS)
+	if (FIELD_GET(ARM_SMMU_S2CR_TYPE, reg) != S2CR_TYPE_BYPASS) {
 		smmu->qcom_bypass_quirk = true;
 
+		/*
+		 * With firmware ignoring writes of type FAULT, booting the
+		 * Linux kernel with disable_bypass disabled (i.e. "enable
+		 * bypass") the initialization during probe will leave mappings
+		 * in an inconsistent state. Avoid this by configuring all
+		 * S2CRs to BYPASS.
+		 */
+		for (i = 0; i < smmu->num_mapping_groups; i++) {
+			smmu->s2crs[i].type = S2CR_TYPE_BYPASS;
+			smmu->s2crs[i].privcfg = S2CR_PRIVCFG_DEFAULT;
+			smmu->s2crs[i].cbndx = 0xff;
+			smmu->s2crs[i].count = 0;
+		}
+	}
+
 	return 0;
 }
 
-- 
2.26.2