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From: Muchun Song <muchun.song@linux.dev>
To: Dev Jain <dev.jain@arm.com>
Cc: osalvador@suse.de, akpm@linux-foundation.org, ljs@kernel.org,
	david@kernel.org, liam@infradead.org, riel@surriel.com,
	vbabka@kernel.org, harry@kernel.org, jannh@google.com,
	lance.yang@linux.dev, kas@kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, rcampbell@nvidia.com,
	apopple@nvidia.com, ziy@nvidia.com, matthew.brost@intel.com,
	joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com,
	gourry@gourry.net, ying.huang@linux.alibaba.com,
	j-nomura@ce.jp.nec.com, nao.horiguchi@gmail.com,
	ak@linux.intel.com, mel@csn.ul.ie, pfalcato@suse.de,
	jpoimboe@kernel.org, dave.hansen@intel.com, tglx@kernel.org,
	catalin.marinas@arm.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com,
	anshuman.khandual@arm.com
Subject: Re: [PATCH v2 6/6] mm/mprotect: use huge_ptep_get() for hugetlb
Date: Thu, 2 Jul 2026 16:30:44 +0800	[thread overview]
Message-ID: <05E75034-5478-42C2-A4E2-BAA6C32A485B@linux.dev> (raw)
In-Reply-To: <20260702051341.126509-7-dev.jain@arm.com>



> On Jul 2, 2026, at 13:13, Dev Jain <dev.jain@arm.com> wrote:
> 
> prot_none_hugetlb_entry() is the hugetlb callback for the early
> mprotect(PROT_NONE) PFN permission walk on x86.
> 
> The callback passes the decoded PFN to pfn_modify_allowed(). For a
> hugetlb callback, the pte pointer refers to a hugetlb entry. On
> architectures where hugetlb entries need huge_ptep_get(), reading that
> entry with ptep_get() can make the permission check use the wrong PFN.
> 
> Use huge_ptep_get() before decoding the hugetlb PFN.
> 
> Currently there is no path which can trigger a bug: huge_ptep_get() is a
> simple ptep_get() for x86, and the prot_none walk occurs only for x86.
> 
> So no need to backport - use the correct helper anyways.
> 
> Fixes: 42e4089c7890 ("x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings")
> Signed-off-by: Dev Jain <dev.jain@arm.com>

Reviewed-by: Muchun Song <muchun.song@linux.dev>

Thanks.

  parent reply	other threads:[~2026-07-02  8:31 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-02  5:13 [PATCH v2 0/6] Fix incorrect access of hugetlb pte entries Dev Jain
2026-07-02  5:13 ` [PATCH v2 1/6] arm64: make huge_ptep_get handled unaligned addresses Dev Jain
2026-07-02 15:28   ` David Hildenbrand (Arm)
2026-07-02  5:13 ` [PATCH v2 2/6] mm/rmap: use huge_ptep_get() in try_to_unmap_one() Dev Jain
2026-07-02  8:47   ` Muchun Song
2026-07-02  9:08     ` Dev Jain
2026-07-02  9:35       ` Muchun Song
2026-07-02 15:30         ` David Hildenbrand (Arm)
2026-07-02 15:32   ` David Hildenbrand (Arm)
2026-07-02  5:13 ` [PATCH v2 3/6] mm/rmap: use huge_ptep_get() in try_to_migrate_one() Dev Jain
2026-07-02 15:34   ` David Hildenbrand (Arm)
2026-07-02  5:13 ` [PATCH v2 4/6] mm/migrate: use huge_ptep_get() in remove_migration_pte() Dev Jain
2026-07-02 15:44   ` David Hildenbrand (Arm)
2026-07-02  5:13 ` [PATCH v2 5/6] mm/page_vma_mapped: use huge_ptep_get() for hugetlb Dev Jain
2026-07-02  8:33   ` Muchun Song
2026-07-02 15:44   ` David Hildenbrand (Arm)
2026-07-02  5:13 ` [PATCH v2 6/6] mm/mprotect: " Dev Jain
2026-07-02  5:18   ` Dev Jain
2026-07-02  8:29     ` Muchun Song
2026-07-02  8:30   ` Muchun Song [this message]
2026-07-02 15:47   ` David Hildenbrand (Arm)

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