linux-kernel - [PATCH] ACPI: bounds check IRQ to prevent memory corruption

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Message-ID: <20080801215755.4761.92512.stgit@tigger.helgaas>
Date:	Fri, 01 Aug 2008 15:58:17 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Bjorn Helgaas <bjorn.helgaas@...com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Natalie Protasevich <protasnb@...il.com>,
	Jack Steiner <steiner@....com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ACPI: bounds check IRQ to prevent memory corruption


acpi_penalize_isa_irq() should validate irq before using it to
index the acpi_irq_penalty[] table.

Here's the path I'm concerned about:

    pnpacpi_parse_allocated_irqresource()
    {
	...
	irq = acpi_register_gsi(gsi, triggering, polarity);
	if (irq >= 0)
		pcibios_penalize_isa_irq(irq, 1);

There's no guarantee that acpi_register_gsi() will return an IRQ
within the bounds of acpi_irq_penalty[].

I have not seen a failure I can attribute to this.  However,
ACPI_MAX_IRQS is only 256, and I'm pretty sure ia64 can have
IRQs larger than that.

I think this should go in 2.6.27.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@...com>
---

 drivers/acpi/pci_link.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)


diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
index 89f3b2a..cf47805 100644
--- a/drivers/acpi/pci_link.c
+++ b/drivers/acpi/pci_link.c
@@ -849,7 +849,7 @@ static int __init acpi_irq_penalty_update(char *str, int used)
 		if (irq < 0)
 			continue;
 
-		if (irq >= ACPI_MAX_IRQS)
+		if (irq >= ARRAY_SIZE(acpi_irq_penalty))
 			continue;
 
 		if (used)
@@ -872,10 +872,12 @@ static int __init acpi_irq_penalty_update(char *str, int used)
  */
 void acpi_penalize_isa_irq(int irq, int active)
 {
-	if (active)
-		acpi_irq_penalty[irq] += PIRQ_PENALTY_ISA_USED;
-	else
-		acpi_irq_penalty[irq] += PIRQ_PENALTY_PCI_USING;
+	if (irq >= 0 && irq < ARRAY_SIZE(acpi_irq_penalty)) {
+		if (active)
+			acpi_irq_penalty[irq] += PIRQ_PENALTY_ISA_USED;
+		else
+			acpi_irq_penalty[irq] += PIRQ_PENALTY_PCI_USING;
+	}
 }
 
 /*

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