From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794272868; b=ImRAstslli/Fd1zbsJhA1l7jJ2AWyXnzE2xPWsZdOrs9y4yo/7271IBQ9RHZ+BFHkquv tpzVAYlow0ra7+tmmeSlkfG07RSWDrUDEDEtwy3TBC9hJaErSL2iBASr4+E8L0M7H5OBb 71HM17UvgFhgHWI0F147ea8OScsygSo2kc6w0bg1VUQ7ZLjiE0vr+SYxOgNvEZFEwKdQL Hh23wN/lDlSxdsSGZToa0/rEdo6vXviGQ1aQ40V61lf6t2zUGnBc5ei2iYzE7b5GmQs1A AcEfncW/GOSieYdRQ3am69+NjvkY30vczR37RpWRz8vIqt7iPCVQhe8JH3hLEKVy6AQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794272868; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=ZQiwWe+Yxe6ObHr8d9IRabLfglTi1D0sahuifWR7rMA=; b=rUqloa68wzvbd6NLH9yLfUlqr3vmTHFVs/xoTi1G3lt8AuLggm23napk6ZSuok23NSru eolE9Rtprwmo08VkH9k+VQCC73dRtnFn/IrKkTlU+6LsmUhbiKd2XshcXQlDjbpNucoiP pzcidsoBglhCuwWZt0w2Fe9xGuMFnbDRo9RGpTCRWjFxVnEo8egimwSie41+gxX9DZOUF 4PsX5EAC4y7dM0KNTB4nZrQyBBxWgW/jsKxr2TvSRmC9t4RFQouD1iOKDJLdk3Wc56rPo TLCKmm+uZWSN54/fwfuy7liR6ADvEIFe1srRhHk1WY5to116+Lz+jKJJDR9F4yufnHg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PsGtjCdq; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7BA41606A321 for ; Tue, 10 Nov 2026 01:07:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=PsGtjCdq Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97BCF1F0089F; Tue, 10 Nov 2026 01:07:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794272868; bh=ZQiwWe+Yxe6ObHr8d9IRabLfglTi1D0sahuifWR7rMA=; h=From:To:Cc:Subject:Date; b=PsGtjCdq5i7olOD/TYbuxC7pXqcdnU0EJB3NVe3uhYJTW/hjG3d9KzRrcXfEbDzWP UgG3P3ILNer5QsBgyNGipgvwJZltmKndeNa/idkVMBzSq2BiSuA98tBowwW8a+N3hG Pme1mVdSBbrbK04NmNiufTaRhmz16ob9vU42q0N4wNQ7F9f0YdvX2SLbtCX1QmtPCh InvPPsZ3IXXwk43mzesiqqN1rInC7BlkxuvMcOG8I/F1yu5+aOwX5QINBQIJgOW/NE 4aRdmLopyiMlceHbHf2eRqg5jwDvFMy0WPIna0sGI3bFCV6p/kMIKZwnSArTnzdkqz cZnxCDHgnC+xw== From: Sasha Levin To: david@kernel.org, akpm@linux-foundation.org, kylebot@openai.com, ljs@kernel.org, kas@kernel.org, baolin.wang@linux.alibaba.com, lance.yang@linux.dev, baohua@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, huang.ying.caritas@gmail.com, ryan.roberts@arm.com, hanchuanhua@oppo.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm: fix address wraparound when scanning large folio PTEs" failed to apply to 6.12-stable tree Date: Mon, 9 Nov 2026 20:07:45 -0500 Message-ID: <20261109200745-failed-6.12-f681d4580d5c@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x f681d4580d5c3c749f623cda722a21aefd3147b3 # git commit -s git send-email --to '' --in-reply-to '20261109200745-failed-6.12-f681d4580d5c@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From f681d4580d5c3c749f623cda722a21aefd3147b3 Mon Sep 17 00:00:00 2001 From: "David Hildenbrand (Arm)" Date: Wed, 14 Oct 2026 20:34:28 +0200 Subject: [PATCH] mm: fix address wraparound when scanning large folio PTEs numa_rebuild_large_mapping() and do_swap_page() can be tricked into generating an address wraparound, crashing the kernel. All that's required is to map a tail page of a large folio close enough to the start/end of the address space to e.g., make unsigned long addr_start = addr - (nr << PAGE_SHIFT); to wrap around. Let's fix it by providing a better helper, folio_scan_range(), that takes care of staying within VMA and page table boundaries while handling possible wraparounds. There are some nasty details, like not being able to use pmd_addr_end() in this context. Add some helpful comments for these cases. Link: https://lore.kernel.org/20261014-folio_pte_scan_range-v2-1-00cf9bbaa364@kernel.org Fixes: d2136d749d76 ("mm: support multi-size THP numa balancing") Fixes: 508758960b8d ("mm: swap: entirely map large folios found in swapcache") Signed-off-by: David Hildenbrand (Arm) Signed-off-by: Andrew Morton Reported-by: Kyle Zeng Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Kiryl Shutsemau (Meta) Reviewed-by: Baolin Wang Reviewed-by: Lance Yang Reviewed-by: Barry Song Cc: Liam R. Howlett Cc: Vlastimil Babka Cc: Mike Rapoport Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Ying Huang Cc: Ryan Roberts Cc: Chuanhua Han Cc: --- mm/memory.c | 50 ++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 36 insertions(+), 14 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 0fb676dd2bd63..591592bc5a941 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4933,6 +4933,34 @@ static void check_swap_exclusive(struct folio *folio, swp_entry_t entry, } while (--nr_pages); } +/* + * Get the address range in which a folio might be mapped, assuming its pages + * are mapped consecutively and the folio page at the given idx is mapped at + * the given address. + */ +static void folio_pte_range(const struct folio *folio, + const struct vm_area_struct *vma, unsigned long addr, + unsigned long idx, unsigned long *start, unsigned long *end) +{ + /* Stay within the page table and VMA boundaries. */ + const unsigned long pmd_start = addr & PMD_MASK; + const unsigned long pmd_end = pmd_start + PMD_SIZE; + const unsigned long lower = max(pmd_start, vma->vm_start); + /* + * We cannot use pmd_addr_end(), as it does not clamp reliably. To + * avoid wraparounds, compute using the inclusive end. + */ + const unsigned long upper = min(pmd_end - 1, vma->vm_end - 1) + 1; + const unsigned long offset = idx << PAGE_SHIFT; + + /* + * Avoid start/end addresses wrapping by not adding/subtracting more + * than the lower/upper limits would allow. + */ + *start = addr - min(addr - lower, offset); + *end = addr + min(upper - addr, folio_size(folio) - offset); +} + /* * We enter with either the VMA lock or the mmap_lock held (see * FAULT_FLAG_VMA_LOCK), and pte mapped but not yet locked. @@ -5121,16 +5149,15 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) address = vmf->address; ptep = vmf->pte; if (folio_test_large(folio) && folio_test_swapcache(folio)) { - int nr = folio_nr_pages(folio); - unsigned long idx = folio_page_idx(folio, page); - unsigned long folio_start = address - idx * PAGE_SIZE; - unsigned long folio_end = folio_start + nr * PAGE_SIZE; + const int nr = folio_nr_pages(folio); + const unsigned long idx = folio_page_idx(folio, page); + unsigned long folio_start, folio_end; pte_t *folio_ptep; pte_t folio_pte; - if (unlikely(folio_start < max(address & PMD_MASK, vma->vm_start))) - goto check_folio; - if (unlikely(folio_end > pmd_addr_end(address, vma->vm_end))) + folio_pte_range(folio, vma, address, idx, &folio_start, + &folio_end); + if (unlikely((folio_end - folio_start) >> PAGE_SHIFT != nr)) goto check_folio; folio_ptep = vmf->pte - idx; @@ -6280,16 +6307,11 @@ static void numa_rebuild_large_mapping(struct vm_fault *vmf, struct vm_area_stru struct folio *folio, pte_t fault_pte, bool ignore_writable, bool pte_write_upgrade) { - int nr = pte_pfn(fault_pte) - folio_pfn(folio); + const unsigned long idx = pte_pfn(fault_pte) - folio_pfn(folio); unsigned long start, end, addr = vmf->address; - unsigned long addr_start = addr - (nr << PAGE_SHIFT); - unsigned long pt_start = ALIGN_DOWN(addr, PMD_SIZE); pte_t *start_ptep; - /* Stay within the VMA and within the page table. */ - start = max3(addr_start, pt_start, vma->vm_start); - end = min3(addr_start + folio_size(folio), pt_start + PMD_SIZE, - vma->vm_end); + folio_pte_range(folio, vma, addr, idx, &start, &end); start_ptep = vmf->pte - ((addr - start) >> PAGE_SHIFT); /* Restore all PTEs' mapping of the large folio */ -- 2.53.0