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 3696E1459FA; Mon, 23 Mar 2026 14:43:48 +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=1774277028; cv=none; b=VdKiza4dUeUMKCA4NlbuJBUa6e6dvY7FXEH0A6CfSBT/3p4UDplLItmJnq0jGhpHaOyxxZ8DprywViFQM8nfgW7wOtU5HahnqLFh9H2nn2QnVama9XFimfWRDwBpC6tR/r2wOlHV7TyVN+iHSNzqmqbUL2vUU6izuRf+L5u/zO0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774277028; c=relaxed/simple; bh=L4MLnQGoxbRwPKvgNDqlFdryrKlV7TwZiyQgezZq9/I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PIg03MoLwiViFUeCnYSzWt8KXDn+JmfjD8CoI9x97QQz+p2EsovL/4RhsZy0N4jz2ZLLYamVMqx2waPndSDVRB4EAgY+cofDcnWkVIBauKBvtXvrOHT9mwCet44V+UmHFjal+uo/DfYro+t1yQh18NQvu/m7xlZFiJYxzLVuJEc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=pgYzjTpt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="pgYzjTpt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98CC2C4CEF7; Mon, 23 Mar 2026 14:43:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774277028; bh=L4MLnQGoxbRwPKvgNDqlFdryrKlV7TwZiyQgezZq9/I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pgYzjTptjx8Sp8cynXAPH3salIJ/qonh4l13V5A/2sjReLFmCSUS1IONC6at6Pack uEBPChyVwk6icMqkgc5omexHKH3+28WgZ10o2dzIlELZWEvSfgrjdEyn6SWbAm7xJL FRyi6YICGwvQnO/O6kcnQgAbq4d9VGar2XH0mFV0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Deepanshu Kartikey , syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com, Lance Yang , "David Hildenbrand (Arm)" , Barry Song , Ackerley Tng , Lorenzo Stoakes , Baolin Wang , Dev Jain , Fangrui Song , Liam Howlett , Nico Pache , Ryan Roberts , Yang Shi , Zi Yan , Andrew Morton Subject: [PATCH 6.12 295/460] mm: thp: deny THP for files on anonymous inodes Date: Mon, 23 Mar 2026 14:44:51 +0100 Message-ID: <20260323134533.735545970@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260323134526.647552166@linuxfoundation.org> References: <20260323134526.647552166@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Deepanshu Kartikey commit dd085fe9a8ebfc5d10314c60452db38d2b75e609 upstream. file_thp_enabled() incorrectly allows THP for files on anonymous inodes (e.g. guest_memfd and secretmem). These files are created via alloc_file_pseudo(), which does not call get_write_access() and leaves inode->i_writecount at 0. Combined with S_ISREG(inode->i_mode) being true, they appear as read-only regular files when CONFIG_READ_ONLY_THP_FOR_FS is enabled, making them eligible for THP collapse. Anonymous inodes can never pass the inode_is_open_for_write() check since their i_writecount is never incremented through the normal VFS open path. The right thing to do is to exclude them from THP eligibility altogether, since CONFIG_READ_ONLY_THP_FOR_FS was designed for real filesystem files (e.g. shared libraries), not for pseudo-filesystem inodes. For guest_memfd, this allows khugepaged and MADV_COLLAPSE to create large folios in the page cache via the collapse path, but the guest_memfd fault handler does not support large folios. This triggers WARN_ON_ONCE(folio_test_large(folio)) in kvm_gmem_fault_user_mapping(). For secretmem, collapse_file() tries to copy page contents through the direct map, but secretmem pages are removed from the direct map. This can result in a kernel crash: BUG: unable to handle page fault for address: ffff88810284d000 RIP: 0010:memcpy_orig+0x16/0x130 Call Trace: collapse_file hpage_collapse_scan_file madvise_collapse Secretmem is not affected by the crash on upstream as the memory failure recovery handles the failed copy gracefully, but it still triggers confusing false memory failure reports: Memory failure: 0x106d96f: recovery action for clean unevictable LRU page: Recovered Check IS_ANON_FILE(inode) in file_thp_enabled() to deny THP for all anonymous inode files. Link: https://syzkaller.appspot.com/bug?extid=33a04338019ac7e43a44 Link: https://lore.kernel.org/linux-mm/CAEvNRgHegcz3ro35ixkDw39ES8=U6rs6S7iP0gkR9enr7HoGtA@mail.gmail.com Link: https://lkml.kernel.org/r/20260214001535.435626-1-kartikey406@gmail.com Fixes: 7fbb5e188248 ("mm: remove VM_EXEC requirement for THP eligibility") Signed-off-by: Deepanshu Kartikey Reported-by: syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=33a04338019ac7e43a44 Tested-by: syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com Tested-by: Lance Yang Acked-by: David Hildenbrand (Arm) Reviewed-by: Barry Song Reviewed-by: Ackerley Tng Tested-by: Ackerley Tng Reviewed-by: Lorenzo Stoakes Cc: Baolin Wang Cc: Dev Jain Cc: Fangrui Song Cc: Liam Howlett Cc: Nico Pache Cc: Ryan Roberts Cc: Yang Shi Cc: Zi Yan Cc: Signed-off-by: Andrew Morton [ Ackerley: we don't have IS_ANON_FILE() yet. As guest_memfd does not apply yet, simply check for secretmem explicitly. ] Signed-off-by: Ackerley Tng Reviewed-by: David Hildenbrand (Arm) Signed-off-by: Greg Kroah-Hartman --- include/linux/huge_mm.h | 4 ++++ 1 file changed, 4 insertions(+) --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -7,6 +7,7 @@ #include /* only for vma_is_dax() */ #include +#include vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf); int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, @@ -262,6 +263,9 @@ static inline bool file_thp_enabled(stru inode = vma->vm_file->f_inode; + if (secretmem_mapping(inode->i_mapping)) + return false; + return (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS)) && !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode); }