From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 CA25815624B; Tue, 17 Mar 2026 19:50:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773777032; cv=none; b=Dg5UjnaV2yQR0GMUpAVHG1MuflUNwU/xAaY3+C/C/fLCtmttYHQbd++sE5bUjkwEvCjfOfsrBJjlJ3uIwCyGb9+BpK2iTMsXOGD407OfTQU4Ncx2H6RFZxeRyOBK4HJMR+mKTeKrE/6bG/0ILwIDgim+3wyMK/tAtH/ycJieeCw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773777032; c=relaxed/simple; bh=mw3UWYrIDInNC8rvnn2qTkNDP7Ch20Xwj37cxzUohtk=; h=Date:To:From:Subject:Message-Id; b=jB/cf6Km94/lNaAlGNXw250c6UGhtljyDC6LiSCIjqHMkwidaiI44KP27u+HVATaA9jkxBxCKmVrfC+chPpGyiTiutGPemJwAFtTyFv3GRMS28hr8QpwyLpOgW7fimtHOLJFTlZ9bPEXwYscfRCIpZbx9aZq8Hahx8Do9JYw948= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=KgFVURgq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="KgFVURgq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F203C4CEF7; Tue, 17 Mar 2026 19:50:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1773777032; bh=mw3UWYrIDInNC8rvnn2qTkNDP7Ch20Xwj37cxzUohtk=; h=Date:To:From:Subject:From; b=KgFVURgqQ8+N4q+TtkyzBG42r3+eBPcCZ8GDavBlqFmtjk+5lVlQP53p/mjDXtSwH CK9BuiigGCAuB6aNOjsw1PXgUty15cq8TkgLoUW3wzdIvaKScyvivxQJk3rrc/0k1P pta2Gn2QYGaOGaydPkdSgR0Rc3sQA85QFxCgS6vo= Date: Tue, 17 Mar 2026 12:50:31 -0700 To: mm-commits@vger.kernel.org,xiangzao@linux.alibaba.com,willy@infradead.org,stable@vger.kernel.org,p.raghav@samsung.com,mcgrof@kernel.org,lorenzo.stoakes@oracle.com,kas@kernel.org,hare@suse.de,djwong@kernel.org,dhowells@redhat.com,dchinner@redhat.com,david@kernel.org,da.gomez@samsung.com,brauner@kernel.org,baolin.wang@linux.alibaba.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-filemap-fix-nr_pages-calculation-overflow-in-filemap_map_pages.patch added to mm-hotfixes-unstable branch Message-Id: <20260317195032.5F203C4CEF7@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: filemap: fix nr_pages calculation overflow in filemap_map_pages() has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-filemap-fix-nr_pages-calculation-overflow-in-filemap_map_pages.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-filemap-fix-nr_pages-calculation-overflow-in-filemap_map_pages.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Baolin Wang Subject: mm: filemap: fix nr_pages calculation overflow in filemap_map_pages() Date: Tue, 17 Mar 2026 17:29:55 +0800 When running stress-ng on my Arm64 machine with v7.0-rc3 kernel, I encountered some very strange crash issues showing up as "Bad page state": " [ 734.496287] BUG: Bad page state in process stress-ng-env pfn:415735fb [ 734.496427] page: refcount:0 mapcount:1 mapping:0000000000000000 index:0x4cf316 pfn:0x415735fb [ 734.496434] flags: 0x57fffe000000800(owner_2|node=1|zone=2|lastcpupid=0x3ffff) [ 734.496439] raw: 057fffe000000800 0000000000000000 dead000000000122 0000000000000000 [ 734.496440] raw: 00000000004cf316 0000000000000000 0000000000000000 0000000000000000 [ 734.496442] page dumped because: nonzero mapcount " After analyzing this page's state, it is hard to understand why the mapcount is not 0 while the refcount is 0, since this page is not where the issue first occurred. By enabling the CONFIG_DEBUG_VM config, I can reproduce the crash as well and captured the first warning where the issue appears: " [ 734.469226] page: refcount:33 mapcount:0 mapping:00000000bef2d187 index:0x81a0 pfn:0x415735c0 [ 734.469304] head: order:5 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [ 734.469315] memcg:ffff000807a8ec00 [ 734.469320] aops:ext4_da_aops ino:100b6f dentry name(?):"stress-ng-mmaptorture-9397-0-2736200540" [ 734.469335] flags: 0x57fffe400000069(locked|uptodate|lru|head|node=1|zone=2|lastcpupid=0x3ffff) ...... [ 734.469364] page dumped because: VM_WARN_ON_FOLIO((_Generic((page + nr_pages - 1), const struct page *: (const struct folio *)_compound_head(page + nr_pages - 1), struct page *: (struct folio *)_compound_head(page + nr_pages - 1))) != folio) [ 734.469390] ------------[ cut here ]------------ [ 734.469393] WARNING: ./include/linux/rmap.h:351 at folio_add_file_rmap_ptes+0x3b8/0x468, CPU#90: stress-ng-mlock/9430 [ 734.469551] folio_add_file_rmap_ptes+0x3b8/0x468 (P) [ 734.469555] set_pte_range+0xd8/0x2f8 [ 734.469566] filemap_map_folio_range+0x190/0x400 [ 734.469579] filemap_map_pages+0x348/0x638 [ 734.469583] do_fault_around+0x140/0x198 ...... [ 734.469640] el0t_64_sync+0x184/0x188 " The code that triggers the warning is: "VM_WARN_ON_FOLIO(page_folio(page + nr_pages - 1) != folio, folio)", which indicates that set_pte_range() tried to map beyond the large folio's size. By adding more debug information, I found that 'nr_pages' had overflowed in filemap_map_pages(), causing set_pte_range() to establish mappings for a range exceeding the folio size, potentially corrupting fields of pages that do not belong to this folio (e.g., page->_mapcount). After above analysis, I think the possible race is as follows: CPU 0 CPU 1 filemap_map_pages() ext4_setattr() //get and lock folio with old inode->i_size next_uptodate_folio() ....... //shrink the inode->i_size i_size_write(inode, attr->ia_size); //calculate the end_pgoff with the new inode->i_size file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1; end_pgoff = min(end_pgoff, file_end); ...... //nr_pages can be overflowed, cause xas.xa_index > end_pgoff end = folio_next_index(folio) - 1; nr_pages = min(end, end_pgoff) - xas.xa_index + 1; ...... //map large folio filemap_map_folio_range() ...... //truncate folios truncate_pagecache(inode, inode->i_size); To fix this issue, move the 'end_pgoff' calculation before next_uptodate_folio(), so the retrieved folio stays consistent with the file end to avoid 'nr_pages' calculation overflow. After this patch, the crash issue is gone. Link: https://lkml.kernel.org/r/1cf1ac59018fc647a87b0dad605d4056a71c14e4.1773739704.git.baolin.wang@linux.alibaba.com Fixes: 743a2753a02e ("filemap: cap PTE range to be created to allowed zero fill in folio_map_range()") Signed-off-by: Baolin Wang Reported-by: Yuanhe Shu Tested-by: Yuanhe Shu Acked-by: Kiryl Shutsemau (Meta) Acked-by: David Hildenbrand (Arm) Cc: Christian Brauner Cc: Daniel Gomez Cc: "Darrick J. Wong" Cc: Dave Chinner Cc: David Howells Cc: Hannes Reinecke Cc: Lorenzo Stoakes Cc: Luis Chamberalin Cc: Matthew Wilcox (Oracle) Cc: Pankaj Raghav Cc: Signed-off-by: Andrew Morton --- mm/filemap.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/mm/filemap.c~mm-filemap-fix-nr_pages-calculation-overflow-in-filemap_map_pages +++ a/mm/filemap.c @@ -3883,14 +3883,19 @@ vm_fault_t filemap_map_pages(struct vm_f unsigned int nr_pages = 0, folio_type; unsigned short mmap_miss = 0, mmap_miss_saved; + /* + * Recalculate end_pgoff based on file_end before calling + * next_uptodate_folio() to avoid races with concurrent + * truncation. + */ + file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1; + end_pgoff = min(end_pgoff, file_end); + rcu_read_lock(); folio = next_uptodate_folio(&xas, mapping, end_pgoff); if (!folio) goto out; - file_end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE) - 1; - end_pgoff = min(end_pgoff, file_end); - /* * Do not allow to map with PMD across i_size to preserve * SIGBUS semantics. _ Patches currently in -mm which might be from baolin.wang@linux.alibaba.com are mm-filemap-fix-nr_pages-calculation-overflow-in-filemap_map_pages.patch mm-use-inline-helper-functions-instead-of-ugly-macros.patch mm-rename-ptep-pmdp_clear_young_notify-to-ptep-pmdp_test_and_clear_young_notify.patch mm-rmap-add-a-zone_device-folio-warning-in-folio_referenced.patch mm-add-a-batched-helper-to-clear-the-young-flag-for-large-folios.patch mm-support-batched-checking-of-the-young-flag-for-mglru.patch arm64-mm-implement-the-architecture-specific-test_and_clear_young_ptes.patch