linux-kernel - Re: [PATCH] powerpc/pseries/iommu: Don't unset window if it was never set

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Message-ID: <173754932979.1094869.2005290852678611840.b4-ty@linux.ibm.com>
Date: Wed, 22 Jan 2025 18:13:57 +0530
From: Madhavan Srinivasan <maddy@...ux.ibm.com>
To: mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org,
        Shivaprasad G Bhat <sbhat@...ux.ibm.com>
Cc: npiggin@...il.com, christophe.leroy@...roup.eu,
        linux-kernel@...r.kernel.org, vaibhav@...ux.ibm.com,
        vaish123@...ibm.com, stable@...r.kernel.org
Subject: Re: [PATCH] powerpc/pseries/iommu: Don't unset window if it was never set

On Mon, 13 Jan 2025 03:48:55 +0000, Shivaprasad G Bhat wrote:
> On pSeries, when user attempts to use the same vfio container used by
> different iommu group, the spapr_tce_set_window() returns -EPERM
> and the subsequent cleanup leads to the below crash.
> 
>    Kernel attempted to read user page (308) - exploit attempt?
>    BUG: Kernel NULL pointer dereference on read at 0x00000308
>    Faulting instruction address: 0xc0000000001ce358
>    Oops: Kernel access of bad area, sig: 11 [#1]
>    NIP:  c0000000001ce358 LR: c0000000001ce05c CTR: c00000000005add0
>    <snip>
>    NIP [c0000000001ce358] spapr_tce_unset_window+0x3b8/0x510
>    LR [c0000000001ce05c] spapr_tce_unset_window+0xbc/0x510
>    Call Trace:
>      spapr_tce_unset_window+0xbc/0x510 (unreliable)
>      tce_iommu_attach_group+0x24c/0x340 [vfio_iommu_spapr_tce]
>      vfio_container_attach_group+0xec/0x240 [vfio]
>      vfio_group_fops_unl_ioctl+0x548/0xb00 [vfio]
>      sys_ioctl+0x754/0x1580
>      system_call_exception+0x13c/0x330
>      system_call_vectored_common+0x15c/0x2ec
>    <snip>
>    --- interrupt: 3000
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/pseries/iommu: Don't unset window if it was never set
      https://git.kernel.org/powerpc/c/17391cb2613b82f8c405570fea605af3255ff8d2

Thanks