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    Subject[PATCH v2] x86: Don't allow nr_irqs > NR_IRQS
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    On some systems probe_nr_irqs() can return a value larger than
    NR_IRQS. This will lead to probe_irq_on() overrunning the irq_desc
    array.

    Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
    ---
    arch/x86/kernel/io_apic.c | 2 ++
    1 files changed, 2 insertions(+), 0 deletions(-)
    
    I hit this when running net-next-2.6 (close to 2.6.28-rc3) on a
    Supermicro dual Xeon system. NR_IRQS is 224 but probe_nr_irqs() detects
    5 IOAPICs and returns 240. Here are the log messages:

    Tue Nov 4 16:53:47 2008 ACPI: IOAPIC (id[0x01] address[0xfec00000] gsi_base[0])
    Tue Nov 4 16:53:47 2008 IOAPIC[0]: apic_id 1, version 32, address 0xfec00000, GSI 0-23
    Tue Nov 4 16:53:47 2008 ACPI: IOAPIC (id[0x02] address[0xfec81000] gsi_base[24])
    Tue Nov 4 16:53:47 2008 IOAPIC[1]: apic_id 2, version 32, address 0xfec81000, GSI 24-47
    Tue Nov 4 16:53:47 2008 ACPI: IOAPIC (id[0x03] address[0xfec81400] gsi_base[48])
    Tue Nov 4 16:53:47 2008 IOAPIC[2]: apic_id 3, version 32, address 0xfec81400, GSI 48-71
    Tue Nov 4 16:53:47 2008 ACPI: IOAPIC (id[0x04] address[0xfec82000] gsi_base[72])
    Tue Nov 4 16:53:47 2008 IOAPIC[3]: apic_id 4, version 32, address 0xfec82000, GSI 72-95
    Tue Nov 4 16:53:47 2008 ACPI: IOAPIC (id[0x05] address[0xfec82400] gsi_base[96])
    Tue Nov 4 16:53:47 2008 IOAPIC[4]: apic_id 5, version 32, address 0xfec82400, GSI 96-119
    Tue Nov 4 16:53:47 2008 ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 high edge)
    Tue Nov 4 16:53:47 2008 ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
    Tue Nov 4 16:53:47 2008 Enabling APIC mode: Flat. Using 5 I/O APICs

    I have added a WARN_ON() as suggested by Yinghai Lu.

    Ben.

    diff --git a/arch/x86/kernel/io_apic.c b/arch/x86/kernel/io_apic.c
    --- a/arch/x86/kernel/io_apic.c
    +++ b/arch/x86/kernel/io_apic.c
    @@ -3611,6 +3611,8 @@ int __init probe_nr_irqs(void)
    /* something wrong ? */
    if (nr < nr_min)
    nr = nr_min;
    + if (WARN_ON(nr > NR_IRQS))
    + nr = NR_IRQS;

    return nr;
    }
    --
    Ben Hutchings, Senior Software Engineer, Solarflare Communications
    Not speaking for my employer; that's the marketing department's job.
    They asked us to note that Solarflare product names are trademarked.

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