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([2a01:599:901:4a65:f2e2:845:f3d2:404d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-40fc5603381sm29816097f8f.31.2025.10.01.08.28.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Oct 2025 08:28:51 -0700 (PDT) Message-ID: <48ed62b1-cceb-4bce-923c-25c11dbccc37@redhat.com> Date: Wed, 1 Oct 2025 17:28:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v5 13/18] mm: Map page tables with privileged pkey To: Kevin Brodsky , linux-hardening@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Lorenzo Stoakes , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , Ryan Roberts , Thomas Gleixner , Vlastimil Babka , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org References: <20250815085512.2182322-1-kevin.brodsky@arm.com> <20250815085512.2182322-14-kevin.brodsky@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251001_082857_064009_2ADD30C3 X-CRM114-Status: GOOD ( 20.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 15.08.25 10:55, Kevin Brodsky wrote: Just wondering, should the patch subject be: "mm: protect page tables with privileged pkey" ? At least patch #2 tells me that set_memory_pkey() will set the protection key, and the function is called "kpkeys_protect_pgtable_memory"? Just trying to connect the dots here :) > If CONFIG_KPKEYS_HARDENED_PGTABLES is enabled, map allocated page > table pages using a privileged pkey (KPKEYS_PKEY_PGTABLES), so that > page tables can only be written under guard(kpkeys_hardened_pgtables). > > This patch is a no-op if CONFIG_KPKEYS_HARDENED_PGTABLES is disabled > (default). > > Signed-off-by: Kevin Brodsky > --- > include/linux/mm.h | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index d9371d992033..4880cb7a4cb9 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -34,6 +34,7 @@ > #include > #include > #include > +#include > > struct mempolicy; > struct anon_vma; > @@ -2979,6 +2980,8 @@ static inline bool __pagetable_ctor(struct ptdesc *ptdesc) > > __folio_set_pgtable(folio); > lruvec_stat_add_folio(folio, NR_PAGETABLE); > + if (kpkeys_protect_pgtable_memory(folio)) > + return false; > return true; > } > > @@ -2989,6 +2992,7 @@ static inline void pagetable_dtor(struct ptdesc *ptdesc) > ptlock_free(ptdesc); > __folio_clear_pgtable(folio); > lruvec_stat_sub_folio(folio, NR_PAGETABLE); > + kpkeys_unprotect_pgtable_memory(folio); This is all rather nasty. Not your fault. In the near future page tables will not be folios, and the whole ptdesc_folio() conversion will not make any sense. Likely you should make kpkeys_protect_pgtable_memory() etc. consume an address range, or a page range right from the start. -- Cheers David / dhildenb