The patch titled Subject: secretmem: fix unhandled fault in truncate has been added to the -mm mm-hotfixes-unstable branch. Its filename is secretmem-fix-unhandled-fault-in-truncate.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Mike Rapoport rppt@linux.ibm.com Subject: secretmem: fix unhandled fault in truncate Date: Thu, 7 Jul 2022 19:56:50 +0300

syzkaller reports the following issue:

BUG: unable to handle page fault for address: ffff888021f7e005 PGD 11401067 P4D 11401067 PUD 11402067 PMD 21f7d063 PTE 800fffffde081060 Oops: 0002 [#1] PREEMPT SMP KASAN CPU: 0 PID: 3761 Comm: syz-executor281 Not tainted 5.19.0-rc4-syzkaller-00014-g941e3e791269 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:memset_erms+0x9/0x10 arch/x86/lib/memset_64.S:64 Code: c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 <f3> aa 4c 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 01 RSP: 0018:ffffc9000329fa90 EFLAGS: 00010202 RAX: 0000000000000000 RBX: 0000000000001000 RCX: 0000000000000ffb RDX: 0000000000000ffb RSI: 0000000000000000 RDI: ffff888021f7e005 RBP: ffffea000087df80 R08: 0000000000000001 R09: ffff888021f7e005 R10: ffffed10043efdff R11: 0000000000000000 R12: 0000000000000005 R13: 0000000000000000 R14: 0000000000001000 R15: 0000000000000ffb FS: 00007fb29d8b2700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffff888021f7e005 CR3: 0000000026e7b000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> zero_user_segments include/linux/highmem.h:272 [inline] folio_zero_range include/linux/highmem.h:428 [inline] truncate_inode_partial_folio+0x76a/0xdf0 mm/truncate.c:237 truncate_inode_pages_range+0x83b/0x1530 mm/truncate.c:381 truncate_inode_pages mm/truncate.c:452 [inline] truncate_pagecache+0x63/0x90 mm/truncate.c:753 simple_setattr+0xed/0x110 fs/libfs.c:535 secretmem_setattr+0xae/0xf0 mm/secretmem.c:170 notify_change+0xb8c/0x12b0 fs/attr.c:424 do_truncate+0x13c/0x200 fs/open.c:65 do_sys_ftruncate+0x536/0x730 fs/open.c:193 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 RIP: 0033:0x7fb29d900899 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fb29d8b2318 EFLAGS: 00000246 ORIG_RAX: 000000000000004d RAX: ffffffffffffffda RBX: 00007fb29d988408 RCX: 00007fb29d900899 RDX: 00007fb29d900899 RSI: 0000000000000005 RDI: 0000000000000003 RBP: 00007fb29d988400 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb29d98840c R13: 00007ffca01a23bf R14: 00007fb29d8b2400 R15: 0000000000022000 </TASK> Modules linked in: CR2: ffff888021f7e005 ---[ end trace 0000000000000000 ]---

Eric Biggers suggested that this happens when secretmem_setattr()->simple_setattr() races with secretmem_fault() so that a page that is faulted in by secretmem_fault() (and thus removed from the direct map) is zeroed by inode truncation right afterwards.

Since do_truncate() takes inode_lock(), adding inode_lock_shared() to secretmem_fault() prevents the race.

Link: https://lkml.kernel.org/r/20220707165650.248088-1-rppt@kernel.org Reported-by: syzbot+9bd2b7adbd34b30b87e4@syzkaller.appspotmail.com Signed-off-by: Mike Rapoport rppt@linux.ibm.com Suggested-by: Eric Biggers ebiggers@kernel.org Cc: Axel Rasmussen axelrasmussen@google.com Cc: Eric Biggers ebiggers@kernel.org Cc: Hillf Danton hdanton@sina.com Cc: Matthew Wilcox willy@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/secretmem.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)

--- a/mm/secretmem.c~secretmem-fix-unhandled-fault-in-truncate +++ a/mm/secretmem.c @@ -55,22 +55,28 @@ static vm_fault_t secretmem_fault(struct gfp_t gfp = vmf->gfp_mask; unsigned long addr; struct page *page; + vm_fault_t ret; int err;

if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) return vmf_error(-EINVAL);

+ inode_lock_shared(inode); + retry: page = find_lock_page(mapping, offset); if (!page) { page = alloc_page(gfp | __GFP_ZERO); - if (!page) - return VM_FAULT_OOM; + if (!page) { + ret = VM_FAULT_OOM; + goto out; + }

err = set_direct_map_invalid_noflush(page); if (err) { put_page(page); - return vmf_error(err); + ret = vmf_error(err); + goto out; }

__SetPageUptodate(page); @@ -86,7 +92,8 @@ retry: if (err == -EEXIST) goto retry;

- return vmf_error(err); + ret = vmf_error(err); + goto out; }

addr = (unsigned long)page_address(page); @@ -94,7 +101,11 @@ retry: }

vmf->page = page; - return VM_FAULT_LOCKED; + ret = VM_FAULT_LOCKED; + +out: + inode_unlock_shared(inode); + return ret; }

static const struct vm_operations_struct secretmem_vm_ops = { _

Patches currently in -mm which might be from rppt@linux.ibm.com are

secretmem-fix-unhandled-fault-in-truncate.patch csky-drop-definition-of-pte_order.patch csky-drop-definition-of-pgd_order.patch mips-rename-pud_order-to-pud_table_order.patch mips-drop-definitions-of-pte_order.patch mips-rename-pgd_order-to-pgd_table_order.patch nios2-drop-definition-of-pte_order.patch nios2-drop-definition-of-pgd_order.patch loongarch-drop-definition-of-pte_order.patch loongarch-drop-definition-of-pmd_order.patch loongarch-drop-definition-of-pud_order.patch loongarch-drop-definition-of-pgd_order.patch loongarch-drop-definition-of-pgd_order-v2.patch parisc-rename-pgd_order-to-pgd_table_order.patch xtensa-drop-definition-of-pgd_order.patch arm-heads-rename-pmd_order-to-pmd_entry_order.patch