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 A8CE03B6363 for ; Fri, 7 Aug 2026 02:01:21 +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=1786068084; cv=none; b=JvZGio/a0KwawaXnav86mb65Vee0COYfEemVGXnuxLdnH0++2y+54M0R503us/LLg8jMneunEMSJazFL8mkncU2yePjFVp8Qonh+oCVCrOnI0m9XwuL/LoDTyvUbLQKN+dVOQfo8rujGhgOBJu6eCi3YOgAoru/nqtvj3l6Hsv4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786068084; c=relaxed/simple; bh=RzIjR/R1vuVsvdOSAAIye0tqP1bzaSxgvQ6rlOTU6bI=; h=Date:To:From:Subject:Message-Id; b=ca6Q30sdJYIzYaSh+Nx6rNlxj/tP0MAVMWOW0vjNxiH2zU8btDMbmiFiK8ucVhhZdvd5cRuFjq+lEaElYHzB2S3ECLOFse6q/QVALCznVH62fnxNDrXCrJz6owyBV/4LTnagPgwZjouboH8Hnw7nwR026z9GvAehq8pbiYzg0fE= 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=K7HDpQMy; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="K7HDpQMy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 786431F00A3E; Fri, 7 Aug 2026 02:01:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1786068081; bh=N1JuVrzfi9YsSGImS3CqnzR0EQrBVq4KiecwXNSBLQs=; h=Date:To:From:Subject; b=K7HDpQMyC6V94fuf59X8+3l/Z62u8mMMguC6tDvZ8UPFs6fGmk0DPXa+e/8ozXnj/ HrCtPyRAnGevXmTbBOJMGkcg/zy0kAf6mhORZEsbz+rGDZdklDAa8tzkKfxzzlrNhk rD84PctNg9PpoxXXvwU4+p/CX1XIWmtlzmNFh4Qs= Date: Thu, 06 Aug 2026 19:01:21 -0700 To: mm-commits@vger.kernel.org,vbabka@kernel.org,surenb@google.com,rppt@kernel.org,mhocko@suse.com,ljs@kernel.org,liam@infradead.org,david@kernel.org,brendan.jackman@linux.dev,akpm@linux-foundation.org,jackmanb@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-secretmem-dont-allow-highmem-folios.patch removed from -mm tree Message-Id: <20260807020121.786431F00A3E@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The quilt patch titled Subject: mm/secretmem: don't allow highmem folios has been removed from the -mm tree. Its filename was mm-secretmem-dont-allow-highmem-folios.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Brendan Jackman Subject: mm/secretmem: don't allow highmem folios Date: Fri, 17 Jul 2026 09:48:59 +0000 secretmem_fault() allocates a folio with GFP_HIGHUSER and then calls set_direct_map_invalid_noflush() without checking folio_test_highmem(). This causes a warning and process crash (vibe-coded reproducer in Link below): Su[ 30.071284] ------------[ cut here ]------------ ccessfully allocated and mapped 2097152000 bytes at 0x3a449000 Populating memor[ 30.074614] CPA: called for zero pte. vaddr = 0 cpa->vaddr = 0 y... [ 30.078636] WARNING: arch/x86/mm/pat/set_memory.c:1840 at __cpa_process_fault+0x34d/0x360, CPU#5: allocate_secret/570 [ 30.084789] CPU: 5 UID: 0 PID: 570 Comm: allocate_secret Not tainted 7.1.0-14063-g4edcdefd4083-dirty #10 PREEMPTLAZY [ 30.090937] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 [ 30.097543] EIP: __cpa_process_fault+0x34d/0x360 [ 30.100514] Code: ff ff 85 c0 0f 89 7d fe ff ff e9 3d fe ff ff 8b 03 8b 00 c7 04 24 c8 ff 64 c1 89 44 24 08 8b 45 e8 89 44 24 04 e8 53 7 a 00 00 <0f> 0b c7 45 f0 f2 ff ff ff e9 fc fc ff ff 90 8d 74 26 00 55 25 00 [ 30.110829] EAX: 00000000 EBX: f64afe98 ECX: 00000000 EDX: 00000000 [ 30.114799] ESI: 00000000 EDI: f64afe98 EBP: f64afe04 ESP: f64afdcc [ 30.118785] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 EFLAGS: 00010246 [ 30.123020] CR0: 80050033 CR2: 46c48ffc CR3: 038c8000 CR4: 00000690 [ 30.127010] Call Trace: [ 30.129078] __change_page_attr_set_clr+0x5e7/0x870 [ 30.132275] ? console_unlock+0x99/0x130 [ 30.135069] ? irq_work_queue+0x36/0x70 [ 30.137853] ? page_address+0xd3/0xf0 [ 30.140421] set_direct_map_invalid_noflush+0x52/0x60 [ 30.143782] secretmem_fault+0x128/0x210 [ 30.146560] __do_fault+0x25/0x90 [ 30.149053] handle_mm_fault+0x6d1/0xcb0 [ 30.151759] exc_page_fault+0x135/0x3b0 [ 30.154487] ? doublefault_shim+0x150/0x150 [ 30.157416] handle_exception+0x130/0x130 [ 30.160137] EIP: 0x804d29f [ 30.162307] Code: 89 54 08 e1 89 54 08 e5 89 54 08 e9 89 54 08 ed c3 0f b6 44 24 08 89 7c 24 0c 69 c0 01 01 01 01 8b 7c 24 04 f7 c7 0f 0 0 00 00 <89> 44 0f fc 75 0e c1 e9 02 f3 ab 8b 44 24 04 8b 7c 24 0c c3 31 d2 [ 30.172936] EAX: 5a5a5a5a EBX: 00000000 ECX: 0c800000 EDX: 3a449000 [ 30.176927] ESI: 00000000 EDI: 3a449000 EBP: bfbbae18 ESP: bfbbadac [ 30.180897] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00010246 [ 30.185161] ? doublefault_shim+0x150/0x150 [ 30.187979] ---[ end trace 0000000000000000 ]--- Bus error (core dumped) ./allocate_secret_i686 2000M The equivalent bug was pointed out by a local Sashiko instance on https://lore.kernel.org/all/20260410151746.61150-3-kalyazin@amazon.com/ This hasn't been reproduced it on older kernel versions but from code inspection the bug seems to go back to the original introduction in commit 1507f51255c9f ("mm: introduce memfd_secret system call to create "secret" memory areas"). If this configuration has always been broken, there's no need to worry too much about feature regression here. Nonetheless, instead of just completely disabling secretmem under !HIGHMEM, just drop __GFP_HIGHMEM. This means that now where you previously got a crash, instead you'll just see the secretmem process OOM. Could secretmem just support highmem by saying "this isn't in the direct map anyway" and bailing out before the set_direct_map_invalid_noflush()? Maybe. That depends on requirements that are not well-defined (e.g. is it OK that kmap_local_page() is not a NOP for those pages?), and would require some research and deep thinking. Let's "defer" that until an actual usecase arises. Link: https://github.com/bjackman/limmat-kernel-nix/commit/7b2acba2d3a5ef01400d493a155beb1d135b6bb5 Link: https://lore.kernel.org/20260717-secretmem-highmem-v2-1-1f1a961ca91e@google.com Link: https://lore.kernel.org/all/20260704192603.40aa80cf9242b77aa75e8d8d@linux-foundation.org/ Fixes: 1507f51255c9 ("mm: introduce memfd_secret system call to create "secret" memory areas") Signed-off-by: Brendan Jackman Suggested-by: Andrew Morton Acked-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (ARM) Reviewed-by: Mike Rapoport (Microsoft) Cc: Brendan Jackman Cc: Liam R. Howlett Cc: Michal Hocko Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- mm/secretmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/secretmem.c~mm-secretmem-dont-allow-highmem-folios +++ a/mm/secretmem.c @@ -202,7 +202,7 @@ static struct file *secretmem_file_creat if (IS_ERR(file)) goto err_free_inode; - mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER); + mapping_set_gfp_mask(inode->i_mapping, GFP_USER); mapping_set_unevictable(inode->i_mapping); inode->i_op = &secretmem_iops; _ Patches currently in -mm which might be from jackmanb@google.com are