linux-kernel - Re: [PATCH] PCI/MSI: Prevent UAF in error path

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Message-ID: <CAA5qM4Dru8=Eptg96tWzGU018GSivxZYo90cs3az-OxPSBvH6g@mail.gmail.com>
Date:   Wed, 19 Jan 2022 10:54:53 -0800
From:   Tong Zhang <ztong0001@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Marc Zyngier <maz@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>,
        open list <linux-kernel@...r.kernel.org>,
        Bjorn Helgaas <helgaas@...nel.org>
Subject: Re: [PATCH] PCI/MSI: Prevent UAF in error path

On Wed, Jan 19, 2022 at 9:54 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> When the core MSI allocation fails, then the PCI/MSI code uses an already
> freed MSI descriptor to unmask the MSI mask register in order to bring it back
> into reset state.
>
> Remove MSI_FLAG_FREE_MSI_DESCS from the PCI/MSI irqdomain flags and let the
> PCI/MSI code free the MSI descriptors after usage.
>
> Fixes: 0f62d941acf9 ("genirq/msi: Provide msi_domain_alloc/free_irqs_descs_locked()")
> Reported-by: Tong Zhang <ztong0001@...il.com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  drivers/pci/msi/irqdomain.c |    4 ++--
>  drivers/pci/msi/legacy.c    |    1 -
>  2 files changed, 2 insertions(+), 3 deletions(-)
>
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -28,6 +28,7 @@ void pci_msi_teardown_msi_irqs(struct pc
>                 msi_domain_free_irqs_descs_locked(domain, &dev->dev);
>         else
>                 pci_msi_legacy_teardown_msi_irqs(dev);
> +       msi_free_msi_descs(&dev->dev);
>  }
>
>  /**
> @@ -171,8 +172,7 @@ struct irq_domain *pci_msi_create_irq_do
>         if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
>                 pci_msi_domain_update_chip_ops(info);
>
> -       info->flags |= MSI_FLAG_ACTIVATE_EARLY | MSI_FLAG_DEV_SYSFS |
> -                      MSI_FLAG_FREE_MSI_DESCS;
> +       info->flags |= MSI_FLAG_ACTIVATE_EARLY | MSI_FLAG_DEV_SYSFS;
>         if (IS_ENABLED(CONFIG_GENERIC_IRQ_RESERVATION_MODE))
>                 info->flags |= MSI_FLAG_MUST_REACTIVATE;
>
> --- a/drivers/pci/msi/legacy.c
> +++ b/drivers/pci/msi/legacy.c
> @@ -77,5 +77,4 @@ void pci_msi_legacy_teardown_msi_irqs(st
>  {
>         msi_device_destroy_sysfs(&dev->dev);
>         arch_teardown_msi_irqs(dev);
> -       msi_free_msi_descs(&dev->dev);
>  }

Tested-by: Tong Zhang <ztong0001@...il.com>

Tested on my setup, it no longer crashes.
Thanks!
- Tong