From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8AFB033D6F8; Tue, 13 Oct 2026 12:30:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791894658; cv=none; b=L8+jl1LDMjDPa0ncWpLAeq4bv6RhaD986V+wpCfVlvDHLYfoGucv/jzUW9RtSNWV1BrMdLCr4ihQTwcUn3yjQj3biAUFUxFdZyc4iZHVPF+PZD/PoWJP8NSlAH6OF5ibB++yfIEqp5IzE76jlO0tPmiLAuRg7MZcR8HgYPYhosI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791894658; c=relaxed/simple; bh=q6nRAbWGhJmgn8/3tLbirUhaQCaDCSXwvO/2ykqrnTY=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=gA1jsAiEr3TsdK6o57YmOa4Qv//lBkVuKuS05iBxKADgnP2A6hZPUQs5/bGPRkRN+ujqv0F4tfOA5SMlJFLhW3jxUGcCtSw//M8SVOn1WxRhol6qFvJct5hc6mzYBbvjkT/00rKDaHNDPOZd/9nzj+Xw9IWlwTF7T4LnHRCBm3I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gZTRINwc; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gZTRINwc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E3101F00893; Tue, 13 Oct 2026 12:30:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791894657; bh=Xb1hOH7i9YqMB45ChD69mFDwlRw95h31SKU2E12G4YQ=; h=From:Date:Subject:To:Cc; b=gZTRINwczHe7ZL8f1PcBeMY2tu1LxVXEWFrHCNBd59lQhR9MedBrhgfDx9Et3dRi8 f6FoDnd2y7gIFlEctA7LwOEwX5rQdx3x3J5HQp5Yrklf4+XEdg0QPex25WzYeMC1OO M1k18osGBO5pgsWsaWy4NevXyn6+d2hEBOteBitDaa/nZLl2phfi/bBmWuTJ9xy6gn 8oZhn69X+lszyFM30TxsixPD0ZbUkxKWJa6KfgCOO3OuLdLF4En+VtGFC1LKL7CWui CcTg5oUhXYvFReIGCZCWo3RmgJmWLxphKvPMD81i0+t1zysS0NLtXYmLo7XJkmJu7s HTkBgsINt+kzw== From: "David Hildenbrand (Arm)" Date: Tue, 13 Oct 2026 14:30:37 +0200 Subject: [PATCH] mm: fix address wraparound when scanning large folio PTEs Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261013-folio_pte_scan_range-v1-1-c50dc30bf6ad@kernel.org> X-B4-Tracking: v=1; b=H4sIAGwkzmoC/yXM0QpAQBCF4VfRXFOWEl5F2tYYjLSrHaTk3S0uv zrnv0DIMwnU0QWeDhZ2NkDFEeBk7EgJ98GQpVmhUpUng1vY6XUjLWis9t8GCzSqQiyp6iFcV08 Dn1+2aX/L3s2E29uC+34ANex0hHgAAAA= X-Change-ID: 20261013-folio_pte_scan_range-c6ca19cc8e9d To: Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Ying Huang , Baolin Wang , Barry Song , Ryan Roberts , Chuanhua Han , Mike Rapoport , Kiryl Shutsemau , Kyle Zeng Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, "David Hildenbrand (Arm)" X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4181; i=david@kernel.org; h=from:subject:message-id; bh=q6nRAbWGhJmgn8/3tLbirUhaQCaDCSXwvO/2ykqrnTY=; b=owGbwMvMwCF2/OVpCdfQ3ZWMp9WSGLLOqRTY7REJCHv+Oc5wyrsQY85DXHtSTqgvU5xxJCtRs 8/y8Yu5HaUsDGIcDLJiiixBwfcNXr5cV1vtxscMM4eVCWQIAxenAEwkTJfhf2i1y5Xmsthvm1Jc JupN/tP07EzGhtsH+iZfDrue6vPVcSfDH+7NvOdtDjh5Ou/ozjkY8mGRWJ4+X4RO/55zV6dvqIn eyQAA X-Developer-Key: i=david@kernel.org; a=openpgp; fpr=1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A 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_pte_scan_range(), that takes care of staying within VMA and page table boundaries while handling possible wraparounds. Reported-by: Kyle Zeng Fixes: d2136d749d76 ("mm: support multi-size THP numa balancing") Fixes: 508758960b8d ("mm: swap: entirely map large folios found in swapcache") Cc: stable@vger.kernel.org Signed-off-by: David Hildenbrand (Arm) --- mm/memory.c | 43 +++++++++++++++++++++++++++++-------------- 1 file changed, 29 insertions(+), 14 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 1f5d5f7d39cd2..a3823010aa981 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4933,6 +4933,27 @@ 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_scan_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); + const unsigned long upper = min(pmd_end - 1, vma->vm_end - 1) + 1; + const unsigned long offset = idx << PAGE_SHIFT; + + /* Avoid any address wraparounds. */ + *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 +5142,15 @@ 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_scan_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 +6300,11 @@ 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_scan_range(folio, vma, addr, idx, &start, &end); start_ptep = vmf->pte - ((addr - start) >> PAGE_SHIFT); /* Restore all PTEs' mapping of the large folio */ --- base-commit: 634cbf5b794b734c78631b92e381cfc85f357bbe change-id: 20261013-folio_pte_scan_range-c6ca19cc8e9d -- Cheers, David