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=1794632906; b=zpGYBLv3f+A6x8JJUviN6tX8g/aIkGbalRCOnbjQU/+gC39BQEh8MjG7niwfYB6hiwCp VrhqfWnLh2z0ZeGA1uF1f7A8ed+UApwAAR1cF3r43rWgblnuXXUUMsTzzsurrpr8yOgWU CB4drJUFGSHH4pAwIj20ztrNSvxisrvs4v92zVZM8/Wf6azySyCo1R7URKJUYWSGRC8T5 Y6BkFm9S1wG3pePjHs5omFCJiTyPGhterLphA+7Q84vBxcdnWM7PjdzFj8YSIIC0DvoFS 2OH/So2edxhhu3n+PEhRSZ/lVHRdSL/jRYYXBxzfyiI8hz0dd7kAzj4lPSENs6i4hdg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794632906; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=tsL3iwsFx71GaykuCUTIehWzz071WJJ0i9okmw4GtGI=; b=L1prAo+EA7ecOVgmE32E/yObd9kRJ6JxJHc1HQKknEV6+JT5dRe2Qo9paJGt9Anm1h7C LLOvmbLNTJz65zMwn6f2IdTeYdyx+4a89pq0aJTQAeqMtRalagx9+EJygqQH8vfGpQZ8G TuyokI403dJDemmIWKxfswesSMA/DlTPMXgJ1SWXBJ6LcrUlwYoVIh/R/UqN//2aQ+Gsj qGOwlCUyfTHRwz5AzeZAVX6p70zL7/Z9rN+HnOgEJWJ3rtrgB6NkRQAP/e5d7wnpKTq/Z vopFGw/cbnhPFUppPn8P+grraTEgVxx4I4MW9ImOA+wVtk5rsa09Wasefpon+bT+LOw== 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=EYW2Kbv+; 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 5931F606A32D for ; Sat, 14 Nov 2026 05:08:26 +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=EYW2Kbv+ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 32FFD1F000C8; Sat, 14 Nov 2026 05:08:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794632905; bh=tsL3iwsFx71GaykuCUTIehWzz071WJJ0i9okmw4GtGI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EYW2Kbv+6PKesDhrlpDRRqPlTUjWeCQo3lwfSFSwORlk9C2AIxLnIL3tZ237ATwhC r2cH+bwT6ELYO0Xie5ia8rXWD3SpEBlDgbIO1HNR0/hehFE1h7alByZskwWKOE3KNA 7X8WAKt0fyL6/hSOaZbCRZC6XX4UfHXdyLv2TxOr1HcWrQb+tvE42x1nRuEwS78JbS oi2ZaAUO1oY8gKnFw9tRb17gmqTBi+LDlIr2xIZLKvn2SWIs+6UD4b29Ce5nI4MEYs VJzAEegyWjMknSnS7AtLjQm5fMQ73wvK7tixKNKGjfW38hvU/e6yR+WU1bPAvCYeTr kLX7ly4uADY+Q== From: Sasha Levin To: stable@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Andrew Morton , Kyle Zeng , "Lorenzo Stoakes (ARM)" , "Kiryl Shutsemau (Meta)" , Baolin Wang , Lance Yang , Barry Song , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Ying Huang , Ryan Roberts , Chuanhua Han , Sasha Levin Subject: [PATCH 6.18.y 2/2] mm: fix address wraparound when scanning large folio PTEs Date: Sat, 14 Nov 2026 00:08:21 -0500 Message-ID: <20261114050807.3044739-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261114050807.3044739-1-sashal@kernel.org> References: <20261109200351-failed-6.18-f681d4580d5c@kernel.org> <20261114050807.3044739-1-sashal@kernel.org> 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-Transfer-Encoding: 8bit From: "David Hildenbrand (Arm)" [ Upstream commit f681d4580d5c3c749f623cda722a21aefd3147b3 ] 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: Signed-off-by: Sasha Levin --- mm/memory.c | 50 ++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 36 insertions(+), 14 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index c9597d7f8ba0a..e8a5292c5a317 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4604,6 +4604,34 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf) static DECLARE_WAIT_QUEUE_HEAD(swapcache_wq); +/* + * 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. @@ -4861,16 +4889,15 @@ 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; @@ -5963,16 +5990,11 @@ 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