From: Jason Gunthorpe <jgg@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Gregory Price (Meta)" <gourry@gourry.net>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com, leon@kernel.org, david@kernel.org,
kas@kernel.org, dave.hansen@linux.intel.com, bp@alien8.de,
rppt@kernel.org, stable@vger.kernel.org,
"Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Subject: Re: [PATCH] mm/hmm: reject shadow-stack mappings
Date: Sat, 14 Nov 2026 20:00:05 -0400 [thread overview]
Message-ID: <20261115000005.GG3706007@nvidia.com> (raw)
In-Reply-To: <20261113181025.6e8b9475b29c13d29f59e02e@linux-foundation.org>
On Fri, Nov 13, 2026 at 06:10:25PM -0800, Andrew Morton wrote:
> How does this look for an altered changelog?
>
> : On x86, a shadow-stack PTE has its ordinary write bit clear. The CPU
> : rejects ordinary stores to it, but pte_write() reports it writable because
> : shadow-stack instructions can write it. HMM consequently sets
> : HMM_PFN_WRITE, which Nouveau turns into ordinary GPU write permission. A
> : process with GPU access can then overwrite its own shadow stack,
> : potentially corrupting return addresses or bypassing that protection.
> :
> : Reject shadow-stack VMAs in hmm_vma_walk_test(), including read access. A
> : requested fault returns -EFAULT; a snapshot records HMM_PFN_ERROR.
Yes, but it is not just nouveau, RDMA user can do this too and
that is far more common..
Thanks,
Jason
next prev parent reply other threads:[~2026-11-15 0:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-13 19:55 [PATCH] mm/hmm: reject shadow-stack mappings Gregory Price (Meta)
2026-11-13 19:57 ` Lorenzo Stoakes (ARM)
2026-11-13 20:15 ` Gregory Price (Meta)
2026-11-13 20:03 ` David Hildenbrand (Arm)
2026-11-13 20:42 ` Gregory Price (Meta)
2026-11-13 21:19 ` David Hildenbrand (Arm)
2026-11-13 20:03 ` Jason Gunthorpe
2026-11-13 20:41 ` Gregory Price (Meta)
2026-11-14 0:20 ` Jason Gunthorpe
2026-11-14 2:10 ` Andrew Morton
2026-11-15 0:00 ` Jason Gunthorpe [this message]
2026-11-14 7:25 ` Gregory Price (Meta)
2026-11-14 11:11 ` David Hildenbrand (Arm)
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