Re: [tip: x86/urgent] x86/dma: Tear down DMA ops on driver unbind

[Borislav Petkov]

On Thu, Apr 15, 2021 at 09:00:57AM -0000, tip-bot2 for Jean-Philippe Brucker wrote:
> The following commit has been merged into the x86/urgent branch of tip:
> 
> Commit-ID:     9f8614f5567eb4e38579422d38a1bdfeeb648ffc
> Gitweb:        https://git.kernel.org/tip/9f8614f5567eb4e38579422d38a1bdfeeb648ffc
> Author:        Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> AuthorDate:    Wed, 14 Apr 2021 10:26:34 +02:00
> Committer:     Borislav Petkov <bp@xxxxxxx>
> CommitterDate: Thu, 15 Apr 2021 10:27:29 +02:00
> 
> x86/dma: Tear down DMA ops on driver unbind
> 
> Since
> 
>   08a27c1c3ecf ("iommu: Add support to change default domain of an iommu group")
> 
> a user can switch a device between IOMMU and direct DMA through sysfs.
> This doesn't work for AMD IOMMU at the moment because dev->dma_ops is
> not cleared when switching from a DMA to an identity IOMMU domain. The
> DMA layer thus attempts to use the dma-iommu ops on an identity domain,
> causing an oops:
> 
>   # echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/unbind
>   # echo identity > /sys/bus/pci/devices/0000:00:05.0/iommu_group/type
>   # echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/bind
>    ...
>   BUG: kernel NULL pointer dereference, address: 0000000000000028
>    ...
>    Call Trace:
>     iommu_dma_alloc
>     e1000e_setup_tx_resources
>     e1000e_open
> 
> Implement arch_teardown_dma_ops() on x86 to clear the device's dma_ops
> pointer during driver unbind.
> 
>  [ bp: Massage commit message. ]
> 
> Fixes: 08a27c1c3ecf ("iommu: Add support to change default domain of an iommu group")
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> Link: https://lkml.kernel.org/r/20210414082633.877461-1-jean-philippe@xxxxxxxxxx
> ---
>  arch/x86/Kconfig          | 1 +
>  arch/x86/kernel/pci-dma.c | 7 +++++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 2792879..2c90f8d 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -85,6 +85,7 @@ config X86
>  	select ARCH_HAS_STRICT_MODULE_RWX
>  	select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
>  	select ARCH_HAS_SYSCALL_WRAPPER
> +	select ARCH_HAS_TEARDOWN_DMA_OPS	if IOMMU_DMA
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
>  	select ARCH_HAS_DEBUG_WX
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index de234e7..60a4ec2 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -154,3 +154,10 @@ static void via_no_dac(struct pci_dev *dev)
>  DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID,
>  				PCI_CLASS_BRIDGE_PCI, 8, via_no_dac);
>  #endif
> +
> +#ifdef CONFIG_ARCH_HAS_TEARDOWN_DMA_OPS
> +void arch_teardown_dma_ops(struct device *dev)
> +{
> +	set_dma_ops(dev, NULL);
> +}
> +#endif

Nope, sorry, no joy. Zapping it from tip.

With that patch, it fails booting on my test box with messages like
(typing up from video I took):

...
ata: softreset failed (1st FIS failed)
ahci 0000:03:00:1: AMD-Vi: Event logged [IO_PAGE_FAULT domain=...]
ahci 0000:03:00:1: AMD-Vi: Event logged [IO_PAGE_FAULT domain=...]
<--- EOF

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette