Re: [syzbot] stack segment fault in truncate_inode_pages_final

[Dmitry Vyukov]

On Mon, 16 Jan 2023 at 21:47, Jann Horn <jannh@xxxxxxxxxx> wrote:
>
> On Mon, Oct 10, 2022 at 9:42 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> > On Mon, 10 Oct 2022 at 09:35, syzbot
> > <syzbot+0f7dd5852be940800ca4@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    833477fce7a1 Merge tag 'sound-6.1-rc1' of git://git.kernel..
> > > git tree:       upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=17cae158880000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=676645938ad4c02f
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=0f7dd5852be940800ca4
> > > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > Downloadable assets:
> > > disk image: https://storage.googleapis.com/syzbot-assets/f66757bbae28/disk-833477fc.raw.xz
> > > vmlinux: https://storage.googleapis.com/syzbot-assets/50ec5a2788dd/vmlinux-833477fc.xz
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+0f7dd5852be940800ca4@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > +ntfs3 maintainers
>
> There's something deeply wrong with this one; it looks like we're
> trying to execute from an RIP that is not aligned to a full
> instruction. RIP points to the last byte of a CALL instruction. It
> looks like, somehow, while we were somewhere inside
> _raw_spin_unlock_irq, something stomped over RIP. Note how the "Code
> starting with the faulting instruction" section shows an instruction
> that's not visible in the "All code" dump above.


There is a number of stack corruptions reported for ntfs3:

https://lore.kernel.org/all/000000000000bdf37505f1a7fc09@xxxxxxxxxx/
https://lore.kernel.org/all/0000000000004b7b3a05f0bc25f8@xxxxxxxxxx/
https://lore.kernel.org/all/000000000000b7bd0405f059129a@xxxxxxxxxx/

It seems that it somehow very badly corrupts memory and that's not
caught by KASAN.


> Code: 48 c7 c0 40 e8 ca 8d 48 ba 00 00 00 00 00 fc ff df 48 c1 e8 03
> 80 3c 10 00 0f 85 e0 01 00 00 48 8b 05 65 42 6d 0c e8 80 2e 06 <00> 85
> c0 74 17 65 ff 0d 55 c9 a4 7e 0f 85 3e fb ff ff e8 ec ce a2
> All code
> ========
>    0: 48 c7 c0 40 e8 ca 8d mov    $0xffffffff8dcae840,%rax
>    7: 48 ba 00 00 00 00 00 movabs $0xdffffc0000000000,%rdx
>    e: fc ff df
>   11: 48 c1 e8 03          shr    $0x3,%rax
>   15: 80 3c 10 00          cmpb   $0x0,(%rax,%rdx,1)
>   19: 0f 85 e0 01 00 00    jne    0x1ff
>   1f: 48 8b 05 65 42 6d 0c mov    0xc6d4265(%rip),%rax        # 0xc6d428b
>   26:* e8 80 2e 06 00        call   0x62eab <-- trapping instruction
>   2b: 85 c0                test   %eax,%eax
>   2d: 74 17                je     0x46
>   2f: 65 ff 0d 55 c9 a4 7e decl   %gs:0x7ea4c955(%rip)        # 0x7ea4c98b
>   36: 0f 85 3e fb ff ff    jne    0xfffffffffffffb7a
>   3c: e8                    .byte 0xe8
>   3d: ec                    in     (%dx),%al
>   3e: ce                    (bad)
>   3f: a2                    .byte 0xa2
>
> Code starting with the faulting instruction
> ===========================================
>    0: 00 85 c0 74 17 65    add    %al,0x651774c0(%rbp)
>    6: ff 0d 55 c9 a4 7e    decl   0x7ea4c955(%rip)        # 0x7ea4c961
>    c: 0f 85 3e fb ff ff    jne    0xfffffffffffffb50
>   12: e8                    .byte 0xe8
>   13: ec                    in     (%dx),%al
>   14: ce                    (bad)
>   15: a2                    .byte 0xa2
>
> We're interpreting unaligned instruction bytes as "add
> %al,0x651774c0(%rbp)", and RBP is non-canonical (1ffff92000a6cf44), so
> we get a Stack Segment fault.
>
> Unless this is some kind of asynchronous stack UAF decrement, I think
> this might not be NTFS's fault.
>
> > > stack segment: 0000 [#1] PREEMPT SMP KASAN
> > > CPU: 1 PID: 22407 Comm: syz-executor.5 Not tainted 6.0.0-syzkaller-05118-g833477fce7a1 #0
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> > > RIP: 0010:trace_lock_release include/trace/events/lock.h:69 [inline]
> > > RIP: 0010:lock_release+0x55f/0x780 kernel/locking/lockdep.c:5677
> > > Code: 48 c7 c0 40 e8 ca 8d 48 ba 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 e0 01 00 00 48 8b 05 65 42 6d 0c e8 80 2e 06 <00> 85 c0 74 17 65 ff 0d 55 c9 a4 7e 0f 85 3e fb ff ff e8 ec ce a2
> > > RSP: 0018:ffffc90005367a10 EFLAGS: 00010002
> > > RAX: 0000000000000001 RBX: 0000000000000001 RCX: 0000000000000001
> > > RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
> > > RBP: 1ffff92000a6cf44 R08: 0000000000000000 R09: ffffffff8ddf9957
> > > R10: fffffbfff1bbf32a R11: 0000000000000000 R12: ffff888093973498
> > > R13: ffff888093973278 R14: ffffffff8a22b140 R15: ffff8880478d8a00
> > > FS:  00007f9ae3bb2700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
> > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 0000001b2e927000 CR3: 000000003f6b9000 CR4: 00000000003506e0
> > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > Call Trace:
> > >  <TASK>
> > >  __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:157 [inline]
> > >  _raw_spin_unlock_irq+0x12/0x40 kernel/locking/spinlock.c:202
> > >  spin_unlock_irq include/linux/spinlock.h:399 [inline]
> > >  truncate_inode_pages_final+0x5f/0x80 mm/truncate.c:484
> > >  ntfs_evict_inode+0x16/0xa0 fs/ntfs3/inode.c:1741
> > >  evict+0x2ed/0x6b0 fs/inode.c:665
> > >  iput_final fs/inode.c:1748 [inline]
> > >  iput.part.0+0x55d/0x810 fs/inode.c:1774
> > >  iput+0x58/0x70 fs/inode.c:1764
> > >  ntfs_fill_super+0x2e89/0x37f0 fs/ntfs3/super.c:1190
> > >  get_tree_bdev+0x440/0x760 fs/super.c:1323
> > >  vfs_get_tree+0x89/0x2f0 fs/super.c:1530
> > >  do_new_mount fs/namespace.c:3040 [inline]
> > >  path_mount+0x1326/0x1e20 fs/namespace.c:3370
> > >  do_mount fs/namespace.c:3383 [inline]
> > >  __do_sys_mount fs/namespace.c:3591 [inline]
> > >  __se_sys_mount fs/namespace.c:3568 [inline]
> > >  __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
> > >  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+0x63/0xcd
> > > RIP: 0033:0x7f9ae2a8bada
> > > Code: 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 b8 04 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 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:00007f9ae3bb1f88 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
> > > RAX: ffffffffffffffda RBX: 0000000020000200 RCX: 00007f9ae2a8bada
> > > RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f9ae3bb1fe0
> > > RBP: 00007f9ae3bb2020 R08: 00007f9ae3bb2020 R09: 0000000020000000
> > > R10: 0000000000000000 R11: 0000000000000202 R12: 0000000020000000
> > > R13: 0000000020000100 R14: 00007f9ae3bb1fe0 R15: 0000000020000140
> > >  </TASK>
> > > Modules linked in:
> > > ---[ end trace 0000000000000000 ]---
> > > RIP: 0010:trace_lock_release include/trace/events/lock.h:69 [inline]
> > > RIP: 0010:lock_release+0x55f/0x780 kernel/locking/lockdep.c:5677
> > > Code: 48 c7 c0 40 e8 ca 8d 48 ba 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 e0 01 00 00 48 8b 05 65 42 6d 0c e8 80 2e 06 <00> 85 c0 74 17 65 ff 0d 55 c9 a4 7e 0f 85 3e fb ff ff e8 ec ce a2
> > > RSP: 0018:ffffc90005367a10 EFLAGS: 00010002
> > > RAX: 0000000000000001 RBX: 0000000000000001 RCX: 0000000000000001
> > > RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
> > > RBP: 1ffff92000a6cf44 R08: 0000000000000000 R09: ffffffff8ddf9957
> > > R10: fffffbfff1bbf32a R11: 0000000000000000 R12: ffff888093973498
> > > R13: ffff888093973278 R14: ffffffff8a22b140 R15: ffff8880478d8a00
> > > FS:  00007f9ae3bb2700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
> > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 0000001b2e927000 CR3: 000000003f6b9000 CR4: 00000000003506e0
> > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > >
> > >
> > > ---
> > > This report is generated by a bot. It may contain errors.
> > > See https://goo.gl/tpsmEJ for more information about syzbot.
> > > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
> > >
> > > syzbot will keep track of this issue. See:
> > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > >
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> >