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hw/isa/lpc_ich9: Ignore reserved/invalid SCI IRQ

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libFuzzer triggered the following assertion:

  cat << EOF | qemu-system-i386 -M pc-q35-5.0 \
    -nographic -monitor none -serial none \
    -qtest stdio -d guest_errors -trace pci\*
  outl 0xcf8 0x8400f841
  outl 0xcfc 0xebed205d
  outl 0x5d02 0xedf82049
  EOF
  pci_cfg_write ICH9-LPC 31:0 @0x41 <- 0xebed205d
  hw/pci/pci.c:268: int pci_bus_get_irq_level(PCIBus *, int): Assertion `irq_num < bus->nirq' failed.

This is because ich9_lpc_sci_irq() returns -1 for reserved
(illegal) values, but ich9_lpc_pmbase_sci_update() considers
it valid and store it in a 8-bit unsigned type. Then the 255
value is used as GSI IRQ, resulting in a PIRQ value of 247,
more than ICH9_LPC_NB_PIRQS (8).

Fix by simply ignoring the invalid access (and reporting it):

  pci_cfg_write ICH9-LPC 31:0 @0x41 <- 0xebed205d
  ICH9 LPC: SCI IRQ SEL #3 is reserved
  pci_cfg_read mch 00:0 @0x0 -> 0x8086
  pci_cfg_read mch 00:0 @0x0 -> 0x29c08086
  ...

Cc: qemu-stable@nongnu.org
Reported-by: Alexander Bulekov <alxndr@bu.edu>
Fixes: 8f242cb724 ("ich9: implement SCI_IRQ_SEL register")
BugLink: https://bugs.launchpad.net/qemu/+bug/1878642
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20200717151705.18611-1-f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Philippe Mathieu-Daudé 2020-07-17 17:17:05 +02:00 • committed by Paolo Bonzini
parent f8b8f37463
commit 4177b062fc
2 changed files with 12 additions and 3 deletions
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1
include/hw/i386/ich9.h
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@ -144,6 +144,7 @@ struct ICH9LPCState {
#define ICH9_LPC_PMBASE_BASE_ADDRESS_MASK Q35_MASK(32, 15, 7)
#define ICH9_LPC_PMBASE_RTE 0x1
#define ICH9_LPC_PMBASE_DEFAULT 0x1
#define ICH9_LPC_ACPI_CTRL 0x44
#define ICH9_LPC_ACPI_CTRL_ACPI_EN 0x80
#define ICH9_LPC_ACPI_CTRL_SCI_IRQ_SEL_MASK Q35_MASK(8, 2, 0)