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bh=3MEEK8v1bfnLhoM5ox+LZlMLIGtsmSp29MPld+CwMKk=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Tot9zraTJURJnw5N2IUpFuIBwE+z/e64lle88HA7J+VCC3fLS1BZsjDjPje3s9gtx mhTd1/9PtqQp6F5DyId7iaMHMzccT2G30lSwCXvU+hx3AoGw59oDHndFiNxg82f2NJ PBPHY/gxutAfOHhSVJwJeGW8CS/lQd8p5NIFzRfY= From: Kevin Brodsky Date: Tue, 26 May 2026 12:16:03 +0100 Subject: [PATCH RFC v8 14/24] mm: kpkeys: Protect vmemmap page tables MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260526-kpkeys-v8-14-eaaacdacc67c@arm.com> References: <20260526-kpkeys-v8-0-eaaacdacc67c@arm.com> In-Reply-To: <20260526-kpkeys-v8-0-eaaacdacc67c@arm.com> To: linux-hardening@vger.kernel.org Cc: Kevin Brodsky , Andrew Morton , Andy Lutomirski , Catalin Marinas , Dave Hansen , "David Hildenbrand (Arm)" , Ira Weiny , Jann Horn , Jeff Xu , Joey Gouly , Kees Cook , Linus Walleij , Marc Zyngier , Mark Brown , Matthew Wilcox , Maxwell Bland , "Mike Rapoport (IBM)" , Peter Zijlstra , Pierre Langlois , Quentin Perret , Rick Edgecombe , Ryan Roberts , Vlastimil Babka , Will Deacon , Yang Shi , Yeoreum Yun , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org, Lorenzo Stoakes , Thomas Gleixner X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1779794212; l=4833; i=kevin.brodsky@arm.com; s=20260427; h=from:subject:message-id; bh=3MEEK8v1bfnLhoM5ox+LZlMLIGtsmSp29MPld+CwMKk=; b=vBG5Zuv3HOVHNsnoNF+3P4kSpu/6WZh/D0smiFfnmmsLBMtBrJLanxEpANJIXWhoUNDd6RFd4 54dbwGJva/GDdEXzjpQlmcIJ6UIJcQ3zlP9Q8bFLYiyDlIdC7SVJ/N8 X-Developer-Key: i=kevin.brodsky@arm.com; a=ed25519; pk=N2QG+eJKrvkNovwhhwJhnJ4+ScVfsGCHldmqLfcMTFs= X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 1DAB7140018 X-Stat-Signature: bjzmn4wy4taccdxu7hmqx9kmhkzymxgw X-Rspam-User: X-HE-Tag: 1779794290-406013 X-HE-Meta: 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 fqIQMv7G 8TKcL37Ls2feDiHvaobyhg+lgYrWWlnxXhTAcAldGTHpbGCnL8ya2TECNWyxWGNk4fYD6hKaMr8qRCTMjf3ACbEJ2I1sCF0/YiwVkgbFYxAhh7UIXzd7+OlGYrq5PLHW4FhP/FFEaeaJG83nEkJEULJSPqlYyp7EUd7TbphNwdDv8URaskRnvpm9QYlskrcVpCvW1Bfoj0LTRF6dRU8i5Q+1yx38B2gZidD2Zsth+FHxGQdEe5C3zInfVYDosU1sohywy+M0B0MPJ4VZ0Yrcr2/Bw/g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When the kpkeys_hardened_pgtables feature is enabled, make sure that vmemmap page tables are protected by using: * The standard pagetable_alloc() if the buddy allocator is available, as it already allocates protected memory. * The memblock-based kpkeys allocator for early allocations. These allocators are not NUMA-aware, so the page tables may be allocated on any node. This could potentially incur some overhead on large NUMA systems. The arm64 hotplug code is also amended to use a matching pagetable_free(), ensuring that the pkey is reset when the page tables are freed. x86 already uses pagetable_free() on that path. Unlike in vmemmap_alloc_block(), __GFP_RETRY_MAYFAIL is not used as it isn't justified for allocating page tables - this disables the OOM and we do not have a fallback if we fail to allocate page tables. See previous discussion linked below. Link: https://lore.kernel.org/all/38d2a358-4146-bfc9-2a4f-68ce02f75c94@suse.cz/ Signed-off-by: Kevin Brodsky --- This is a minimal patch to protect vmemmmap page tables. More work may be needed here: * Restoring NUMA awareness * Moving the arm64 change to a separate commit? * General refactoring of how these page tables are allocated: since we are not using the standard per-level functions (e.g. pmd_alloc()), we are not calling pagetable_*_ctor() or ptdesc_set_kernel(). [Maybe that doesn't matter because these page tables can only be freed via vmemmap_free()?] --- arch/arm64/mm/mmu.c | 2 +- mm/sparse-vmemmap.c | 33 +++++++++++++++++++++++++-------- 2 files changed, 26 insertions(+), 9 deletions(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 493310cf0486..dc69553d6326 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1441,7 +1441,7 @@ static void free_hotplug_page_range(struct page *page, size_t size, static void free_hotplug_pgtable_page(struct page *page) { - free_hotplug_page_range(page, PAGE_SIZE, NULL); + pagetable_free(page_ptdesc(page)); } static bool pgtable_range_aligned(unsigned long start, unsigned long end, diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index 6eadb9d116e4..c93f5b9f4a26 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -184,13 +184,29 @@ pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node, return pte; } -static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node) +static void * __meminit vmemmap_alloc_pgtable(int node) { - void *p = vmemmap_alloc_block(size, node); + void *p; + + if (slab_is_available()) { + gfp_t gfp = GFP_KERNEL | __GFP_ZERO; + struct ptdesc *ptdesc = pagetable_alloc(gfp, 0); + + return ptdesc ? ptdesc_address(ptdesc) : NULL; + } + + if (kpkeys_hardened_pgtables_early_enabled()) { + phys_addr_t phys = kpkeys_physmem_pgtable_alloc(); + + p = phys ? phys_to_virt(phys) : NULL; + } else { + p = __earlyonly_bootmem_alloc(node, PAGE_SIZE, PAGE_SIZE, + __pa(MAX_DMA_ADDRESS)); + } if (!p) return NULL; - memset(p, 0, size); + memset(p, 0, PAGE_SIZE); return p; } @@ -199,7 +215,7 @@ pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node) { pmd_t *pmd = pmd_offset(pud, addr); if (pmd_none(*pmd)) { - void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); + void *p = vmemmap_alloc_pgtable(node); if (!p) return NULL; kernel_pte_init(p); @@ -212,7 +228,7 @@ pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node) { pud_t *pud = pud_offset(p4d, addr); if (pud_none(*pud)) { - void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); + void *p = vmemmap_alloc_pgtable(node); if (!p) return NULL; pmd_init(p); @@ -225,7 +241,7 @@ p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node) { p4d_t *p4d = p4d_offset(pgd, addr); if (p4d_none(*p4d)) { - void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); + void *p = vmemmap_alloc_pgtable(node); if (!p) return NULL; pud_init(p); @@ -238,7 +254,7 @@ pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node) { pgd_t *pgd = pgd_offset_k(addr); if (pgd_none(*pgd)) { - void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node); + void *p = vmemmap_alloc_pgtable(node); if (!p) return NULL; pgd_populate_kernel(addr, pgd, p); @@ -351,10 +367,11 @@ static __meminit struct page *vmemmap_get_tail(unsigned int order, struct zone * * memmap_init(). */ - p = vmemmap_alloc_block_zero(PAGE_SIZE, node); + p = vmemmap_alloc_block(PAGE_SIZE, node); if (!p) return NULL; + memset(p, 0, PAGE_SIZE); tail = virt_to_page(p); zone->vmemmap_tails[idx] = tail; -- 2.51.2