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SubjectRE: [PATCH] ARCH: Fix 32-bit x86 MSI-X allocation leakage
Date
From
> On Fri, 25 Apr 2008, PJ Waskiewicz wrote:
> > This bug was introduced in the 2.6.24 i386/x86_64 tree merge, where
>
> Can you please explain what exactly caused the bug.
> Definitely not the move from arch/i386 to arch/x86 as the
> code there was not changed at all and has not be changed since then.
>
> CC'ed Eric as well.

Eric replied with the actual commit during the 2.6.24 merge window that
introduced this bug. The io_apic.c code from the i386 tree did not stay
completely static when it was merged into the x86 io_apic_32.c code.
Here is the commit that Eric identified that introduced the defect:

In particular commit dbeb2be21d678c49a8d8bbf774903df15dd55474
Author: Rusty Russell <rusty@rustcorp.com.au>
Date: Fri Oct 19 20:35:03 2007 +0200

i386: introduce "used_vectors" bitmap which can be used to reserve
vectors.

This simplifies the io_apic.c __assign_irq_vector() logic and
removes
the explicit SYSCALL_VECTOR check, and also allows for vectors to be
reserved by other mechanisms (ie. lguest).

[ tglx: arch/x86 adaptation ]

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Basically the code introduced the test_and_set_bit() on the used_vectors
bitmap, but it didn't have a corresponding clear_bit() on IRQ
destruction.

Cheers,
-PJ Waskiewicz


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