linux-kernel - [PATCH v2 2/2] iommu/vt-d: skip invalid RMRR entries

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Date:   Tue,  7 Jan 2020 14:16:10 -0500
From:   Barret Rhoden <brho@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        Yian Chen <yian.chen@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>
Cc:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        x86@...nel.org
Subject: [PATCH v2 2/2] iommu/vt-d: skip invalid RMRR entries

The VT-d docs specify requirements for the RMRR entries base and end
(called 'Limit' in the docs) addresses.

This commit will cause the DMAR processing to skip any RMRR entries that
do not meet these requirements and mark the firmware as tainted, since
the firmware is giving us junk.

Signed-off-by: Barret Rhoden <brho@...gle.com>
---
 drivers/iommu/intel-iommu.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index a8bb458845bc..32c3c6338a3d 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4315,13 +4315,25 @@ static void __init init_iommu_pm_ops(void)
 static inline void init_iommu_pm_ops(void) {}
 #endif	/* CONFIG_PM */
 
+static int rmrr_validity_check(struct acpi_dmar_reserved_memory *rmrr)
+{
+	if ((rmrr->base_address & PAGE_MASK) ||
+	    (rmrr->end_address <= rmrr->base_address) ||
+	    ((rmrr->end_address - rmrr->base_address + 1) & PAGE_MASK)) {
+		pr_err(FW_BUG "Broken RMRR base: %#018Lx end: %#018Lx\n",
+		       rmrr->base_address, rmrr->end_address);
+		return -EINVAL;
+	}
+	return 0;
+}
+
 int __init dmar_parse_one_rmrr(struct acpi_dmar_header *header, void *arg)
 {
 	struct acpi_dmar_reserved_memory *rmrr;
 	struct dmar_rmrr_unit *rmrru;
 
 	rmrr = (struct acpi_dmar_reserved_memory *)header;
-	if (arch_rmrr_sanity_check(rmrr)) {
+	if (rmrr_validity_check(rmrr) || arch_rmrr_sanity_check(rmrr)) {
 		WARN_TAINT(1, TAINT_FIRMWARE_WORKAROUND,
 			   "Your BIOS is broken; bad RMRR [%#018Lx-%#018Lx]\n"
 			   "BIOS vendor: %s; Ver: %s; Product Version: %s\n",
-- 
2.24.1.735.g03f4e72817-goog