From 98f99394a104cc80296da34a62d4e1ad04127013 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 7 Jul 2025 13:21:11 +0200 Subject: [PATCH] secretmem: use SB_I_NOEXEC Anonymous inodes may never ever be exectuable and the only way to enforce this is to raise SB_I_NOEXEC on the superblock which can never be unset. I've made the exec code yell at anyone who does not abide by this rule. For good measure also kill any pretense that device nodes are supported on the secretmem filesystem. > WARNING: fs/exec.c:119 at path_noexec+0x1af/0x200 fs/exec.c:118, CPU#1: syz-executor260/5835 > Modules linked in: > CPU: 1 UID: 0 PID: 5835 Comm: syz-executor260 Not tainted 6.16.0-rc4-next-20250703-syzkaller #0 PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 > RIP: 0010:path_noexec+0x1af/0x200 fs/exec.c:118 > Code: 02 31 ff 48 89 de e8 f0 b1 89 ff d1 eb eb 07 e8 07 ad 89 ff b3 01 89 d8 5b 41 5e 41 5f 5d c3 cc cc cc cc cc e8 f2 ac 89 ff 90 <0f> 0b 90 e9 48 ff ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c a6 > RSP: 0018:ffffc90003eefbd8 EFLAGS: 00010293 > RAX: ffffffff8235f22e RBX: ffff888072be0940 RCX: ffff88807763bc00 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 > RBP: 0000000000080000 R08: ffff88807763bc00 R09: 0000000000000003 > R10: 0000000000000003 R11: 0000000000000000 R12: 0000000000000011 > R13: 1ffff920007ddf90 R14: 0000000000000000 R15: dffffc0000000000 > FS: 000055556832d380(0000) GS:ffff888125d1e000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f21e34810d0 CR3: 00000000718a8000 CR4: 00000000003526f0 > Call Trace: > > do_mmap+0xa43/0x10d0 mm/mmap.c:472 > vm_mmap_pgoff+0x31b/0x4c0 mm/util.c:579 > ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:607 > do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] > do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 > entry_SYSCALL_64_after_hwframe+0x77/0x7f > RIP: 0033:0x7f21e340a9f9 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 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:00007ffd23ca3468 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f21e340a9f9 > RDX: 0000000000000000 RSI: 0000000000004000 RDI: 0000200000ff9000 > RBP: 00007f21e347d5f0 R08: 0000000000000003 R09: 0000000000000000 > R10: 0000000000000011 R11: 0000000000000246 R12: 0000000000000001 > R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001 Link: https://lore.kernel.org/686ba948.a00a0220.c7b3.0080.GAE@google.com Signed-off-by: Christian Brauner --- mm/secretmem.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/mm/secretmem.c b/mm/secretmem.c index 9a11a38a67708..e042a4a0bc0cf 100644 --- a/mm/secretmem.c +++ b/mm/secretmem.c @@ -261,7 +261,15 @@ err_put_fd: static int secretmem_init_fs_context(struct fs_context *fc) { - return init_pseudo(fc, SECRETMEM_MAGIC) ? 0 : -ENOMEM; + struct pseudo_fs_context *ctx; + + ctx = init_pseudo(fc, SECRETMEM_MAGIC); + if (!ctx) + return -ENOMEM; + + fc->s_iflags |= SB_I_NOEXEC; + fc->s_iflags |= SB_I_NODEV; + return 0; } static struct file_system_type secretmem_fs = { @@ -279,9 +287,6 @@ static int __init secretmem_init(void) if (IS_ERR(secretmem_mnt)) return PTR_ERR(secretmem_mnt); - /* prevent secretmem mappings from ever getting PROT_EXEC */ - secretmem_mnt->mnt_flags |= MNT_NOEXEC; - return 0; } fs_initcall(secretmem_init); -- 2.47.2