linux-kernel - Re: [PATCH v1] genirq/msi: fix crash when handling Multi-MSI

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Message-ID: <87iluh9kgx.ffs@tglx>
Date:   Tue, 18 Jan 2022 15:39:26 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <maz@...nel.org>, Tong Zhang <ztong0001@...il.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] genirq/msi: fix crash when handling Multi-MSI

On Mon, Jan 17 2022 at 11:36, Marc Zyngier wrote:
> On Mon, 17 Jan 2022 10:10:13 +0000,
> Tong Zhang <ztong0001@...il.com> wrote:
>> pci_msi_domain_check_cap (used by ops->msi_check(domain, info, dev))
>> msi_domain_prepare_irqs
>> __msi_domain_alloc_irqs
>> msi_domain_alloc_irqs_descs_locked
>> 
>> What I am suggesting is commit 0f62d941acf9 changed how this return
>> value is being handled and created a UAF
>
> OK, this makes more sense.
>
> But msi_domain_prepare_irqs() shouldn't fail in this case, and we
> should proceed with the allocation of at least one vector, which isn't
> happening here.
>
> Also, if __msi_domain_alloc_irqs() is supposed to return the number of
> irqs allocated, it isn't doing it consistently.
>
> Thomas, can you shed some light on what is the intended behaviour
> here?

Let me stare at it.