linux-kernel - [PATCH 3/3] irqchip/gic-v3: Bounds check redistributor accesses

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Message-Id: <20171011094148.15674-4-punit.agrawal@arm.com>
Date:   Wed, 11 Oct 2017 10:41:48 +0100
From:   Punit Agrawal <punit.agrawal@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Punit Agrawal <punit.agrawal@....com>, marc.zyngier@....com,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 3/3] irqchip/gic-v3: Bounds check redistributor accesses

The kernel crashes while iterating over a redistributor that is
in-correctly sized by the platform firmware or doesn't contain the last
record.

Prevent the crash by checking accesses against the size of the region
provided by the firmware. While we are at it, warn the user about
incorrect region size.

Signed-off-by: Punit Agrawal <punit.agrawal@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
---
 drivers/irqchip/irq-gic-v3.c | 48 ++++++++++++++++++++++++++++++++++++--------
 1 file changed, 40 insertions(+), 8 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index 881d327c53fa..754d936c95e5 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -429,11 +429,21 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *))
 	int i;
 
 	for (i = 0; i < gic_data.nr_redist_regions; i++) {
-		void __iomem *ptr = gic_data.redist_regions[i].redist_base;
 		struct resource *res = &gic_data.redist_regions[i].res;
-		u64 typer;
+		void __iomem *ptr, *base;
+		u64 typer, size, stride;
 		u32 reg;
 
+		ptr = base = gic_data.redist_regions[i].redist_base;
+		size = resource_size(res);
+
+		stride = gic_data.redist_stride ?: SZ_64K * 2;
+		if (ptr + stride > base + size) {
+			pr_warn("Insufficient size for redistributor region @%llx. Skipping\n",
+				res->start);
+			continue;
+		}
+
 		reg = readl_relaxed(ptr + GICR_PIDR2) & GIC_PIDR2_ARCH_MASK;
 		if (reg != GIC_PIDR2_ARCH_GICv3 &&
 		    reg != GIC_PIDR2_ARCH_GICv4) { /* We're in trouble... */
@@ -442,7 +452,28 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *))
 		}
 
 		do {
+			/*
+			 * We can access GICR_TYPER as we have already
+			 * checked that we have atleast 128kB or
+			 * redist_stride
+			 */
 			typer = gic_read_typer(ptr + GICR_TYPER);
+			if (!gic_data.redist_stride &&
+			    (typer & GICR_TYPER_VLPIS)) {
+				/* VLPI_base + reserved page */
+				stride += SZ_64K * 2;
+
+				/*
+				 * We are larger than we thought, do
+				 * we still fit?
+				 */
+				if (ptr + stride > base + size) {
+					pr_warn("No last record found in redistributor region @%llx\n",
+						gic_data.redist_regions[i].res.start);
+					break;
+				}
+			}
+
 			ret = fn(gic_data.redist_regions + i, ptr);
 			if (!ret)
 				return 0;
@@ -450,12 +481,13 @@ static int gic_iterate_rdists(int (*fn)(struct redist_region *, void __iomem *))
 			if (gic_data.redist_regions[i].single_redist)
 				break;
 
-			if (gic_data.redist_stride) {
-				ptr += gic_data.redist_stride;
-			} else {
-				ptr += SZ_64K * 2; /* Skip RD_base + SGI_base */
-				if (typer & GICR_TYPER_VLPIS)
-					ptr += SZ_64K * 2; /* Skip VLPI_base + reserved page */
+			ptr += stride;
+
+			stride = gic_data.redist_stride ?: SZ_64K * 2;
+			if (ptr + stride > base + size) {
+				pr_warn("No last record found in redistributor region @%llx\n",
+					gic_data.redist_regions[i].res.start);
+				break;
 			}
 		} while (!(typer & GICR_TYPER_LAST));
 	}
-- 
2.14.1