Re: general protection fault in security_inode_getattr

Re: general protection fault in security_inode_getattr

[Ondrej Mosnacek]

On Mon, Aug 24, 2020 at 9:37 PM syzbot
<syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com> wrote:
> syzbot has found a reproducer for the following issue on:

Looping in fsdevel and OverlayFS maintainers, as this seems to be
FS/OverlayFS related...

See also original report against 5.8-rc7:
https://lore.kernel.org/linux-security-module/0000000000008caae305ab9a5318@google.com/T/

>
> HEAD commit:    d012a719 Linux 5.9-rc2
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14aa130e900000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=891ca5711a9f1650
> dashboard link: https://syzkaller.appspot.com/bug?extid=f07cc9be8d1d226947ed
> compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=104a650e900000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com
>
> general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
> CPU: 1 PID: 32288 Comm: syz-executor.3 Not tainted 5.9.0-rc2-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:d_backing_inode include/linux/dcache.h:549 [inline]
> RIP: 0010:security_inode_getattr+0x42/0x140 security/security.c:1276
> Code: 1b fe 49 8d 5e 08 48 89 d8 48 c1 e8 03 42 80 3c 38 00 74 08 48 89 df e8 bc b4 5b fe 48 8b 1b 48 83 c3 68 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 9f b4 5b fe 48 8b 1b 48 83 c3 0c
> RSP: 0018:ffffc9000a017750 EFLAGS: 00010202
> RAX: 000000000000000d RBX: 0000000000000068 RCX: ffff888093ec6180
> RDX: 0000000000000000 RSI: ffffc9000a017860 RDI: ffffc9000a017850
> RBP: ffffc9000a017850 R08: dffffc0000000000 R09: ffffc9000a017850
> R10: fffff52001402f0c R11: 0000000000000000 R12: ffffc9000a017860
> R13: 0000000000008401 R14: ffffc9000a017850 R15: dffffc0000000000
> FS:  00007f292d4ef700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b30920074 CR3: 00000000937fd000 CR4: 00000000001506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  vfs_getattr+0x21/0x60 fs/stat.c:121
>  ovl_copy_up_one fs/overlayfs/copy_up.c:850 [inline]
>  ovl_copy_up_flags+0x2ef/0x2a00 fs/overlayfs/copy_up.c:931
>  ovl_maybe_copy_up+0x154/0x180 fs/overlayfs/copy_up.c:963
>  ovl_open+0xa2/0x200 fs/overlayfs/file.c:147
>  do_dentry_open+0x7c8/0x1010 fs/open.c:817
>  do_open fs/namei.c:3251 [inline]
>  path_openat+0x2794/0x3840 fs/namei.c:3368
>  do_filp_open+0x191/0x3a0 fs/namei.c:3395
>  file_open_name+0x321/0x430 fs/open.c:1113
>  acct_on kernel/acct.c:207 [inline]
>  __do_sys_acct kernel/acct.c:286 [inline]
>  __se_sys_acct+0x122/0x6f0 kernel/acct.c:273
>  do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x45d579
> Code: 5d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f292d4eec78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3
> RAX: ffffffffffffffda RBX: 0000000000000700 RCX: 000000000045d579
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000040
> RBP: 000000000118cf70 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
> R13: 00007ffc8e04bc4f R14: 00007f292d4ef9c0 R15: 000000000118cf4c
> Modules linked in:
> ---[ end trace 7e4f1041b188e411 ]---
> RIP: 0010:d_backing_inode include/linux/dcache.h:549 [inline]
> RIP: 0010:security_inode_getattr+0x42/0x140 security/security.c:1276
> Code: 1b fe 49 8d 5e 08 48 89 d8 48 c1 e8 03 42 80 3c 38 00 74 08 48 89 df e8 bc b4 5b fe 48 8b 1b 48 83 c3 68 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 9f b4 5b fe 48 8b 1b 48 83 c3 0c
> RSP: 0018:ffffc9000a017750 EFLAGS: 00010202
> RAX: 000000000000000d RBX: 0000000000000068 RCX: ffff888093ec6180
> RDX: 0000000000000000 RSI: ffffc9000a017860 RDI: ffffc9000a017850
> RBP: ffffc9000a017850 R08: dffffc0000000000 R09: ffffc9000a017850
> R10: fffff52001402f0c R11: 0000000000000000 R12: ffffc9000a017860
> R13: 0000000000008401 R14: ffffc9000a017850 R15: dffffc0000000000
> FS:  00007f292d4ef700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fef820e7000 CR3: 00000000937fd000 CR4: 00000000001506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>

-- 
Ondrej Mosnacek
Software Engineer, Platform Security - SELinux kernel
Red Hat, Inc.

Re: general protection fault in security_inode_getattr

[Miklos Szeredi]

On Mon, Aug 24, 2020 at 11:00 PM Ondrej Mosnacek <omosnace@redhat.com> wrote:
>
> On Mon, Aug 24, 2020 at 9:37 PM syzbot
> <syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com> wrote:
> > syzbot has found a reproducer for the following issue on:
>
> Looping in fsdevel and OverlayFS maintainers, as this seems to be
> FS/OverlayFS related...

Hmm, the oopsing code is always something like:

All code
========
   0: 1b fe                sbb    %esi,%edi
   2: 49 8d 5e 08          lea    0x8(%r14),%rbx
   6: 48 89 d8              mov    %rbx,%rax
   9: 48 c1 e8 03          shr    $0x3,%rax
   d: 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1)
  12: 74 08                je     0x1c
  14: 48 89 df              mov    %rbx,%rdi
  17: e8 bc b4 5b fe        callq  0xfffffffffe5bb4d8
  1c: 48 8b 1b              mov    (%rbx),%rbx
  1f: 48 83 c3 68          add    $0x68,%rbx
  23: 48 89 d8              mov    %rbx,%rax
  26: 48 c1 e8 03          shr    $0x3,%rax
  2a:* 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
  2f: 74 08                je     0x39
  31: 48 89 df              mov    %rbx,%rdi
  34: e8 9f b4 5b fe        callq  0xfffffffffe5bb4d8
  39: 48 8b 1b              mov    (%rbx),%rbx
  3c: 48 83 c3 0c          add    $0xc,%rbx


And that looks (to me) like the unrolled loop in call_int_hook().  I
don't see how that could be related to overlayfs, though it's
definitely interesting why it only triggers from
overlay->vfs_getattr()->security_inode_getattr()...

Thanks,
Miklos

Re: general protection fault in security_inode_getattr

[Dmitry Vyukov]

On Fri, Oct 30, 2020 at 2:02 PM Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> On Mon, Aug 24, 2020 at 11:00 PM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> >
> > On Mon, Aug 24, 2020 at 9:37 PM syzbot
> > <syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com> wrote:
> > > syzbot has found a reproducer for the following issue on:
> >
> > Looping in fsdevel and OverlayFS maintainers, as this seems to be
> > FS/OverlayFS related...
>
> Hmm, the oopsing code is always something like:
>
> All code
> ========
>    0: 1b fe                sbb    %esi,%edi
>    2: 49 8d 5e 08          lea    0x8(%r14),%rbx
>    6: 48 89 d8              mov    %rbx,%rax
>    9: 48 c1 e8 03          shr    $0x3,%rax
>    d: 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1)
>   12: 74 08                je     0x1c
>   14: 48 89 df              mov    %rbx,%rdi
>   17: e8 bc b4 5b fe        callq  0xfffffffffe5bb4d8
>   1c: 48 8b 1b              mov    (%rbx),%rbx
>   1f: 48 83 c3 68          add    $0x68,%rbx
>   23: 48 89 d8              mov    %rbx,%rax
>   26: 48 c1 e8 03          shr    $0x3,%rax
>   2a:* 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
>   2f: 74 08                je     0x39
>   31: 48 89 df              mov    %rbx,%rdi
>   34: e8 9f b4 5b fe        callq  0xfffffffffe5bb4d8
>   39: 48 8b 1b              mov    (%rbx),%rbx
>   3c: 48 83 c3 0c          add    $0xc,%rbx
>
>
> And that looks (to me) like the unrolled loop in call_int_hook().  I
> don't see how that could be related to overlayfs, though it's
> definitely interesting why it only triggers from
> overlay->vfs_getattr()->security_inode_getattr()...


>   26: 48 c1 e8 03          shr    $0x3,%rax
>   2a:* 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction


This access is part of KASAN check. But the original address kernel
tries to access is NULL, so it's not an issue with KASAN.

The line is this:

int security_inode_getattr(const struct path *path)
{
    if (unlikely(IS_PRIVATE(d_backing_inode(path->dentry))))
        return 0;

So it's either path is NULL, or something in d_backing_inode
dereferences NULL path->dentry.

The reproducer does involve overlayfs:

mkdir(&(0x7f0000000240)='./file1\x00', 0x0)
mkdir(&(0x7f0000000300)='./bus\x00', 0x0)
r0 = creat(&(0x7f00000000c0)='./bus/file1\x00', 0x0)
mkdir(&(0x7f0000000080)='./file0\x00', 0x0)
mount$overlay(0x400002, &(0x7f0000000000)='./bus\x00',
&(0x7f0000000100)='overlay\x00', 0x0,
&(0x7f00000003c0)=ANY=[@ANYBLOB='upperdir=./file1,lowerdir=./bus,workdir=./file0,metacopy=on'])
link(&(0x7f0000000200)='./bus/file1\x00', &(0x7f00000002c0)='./bus/file0\x00')
write$RDMA_USER_CM_CMD_RESOLVE_ADDR(r0, 0x0, 0x0)
acct(&(0x7f0000000040)='./bus/file0\x00')

Though, it may be overlayfs-related, or it may be a generic bug that
requires a tricky reproducer and the only reproducer syzbot come up
with happened to involve overlayfs.
But there are 4 reproducers on syzbot dashboard and all of them
involve overlayfs and they are somewhat different. So my bet would be
on overlayfs.

Re: general protection fault in security_inode_getattr

[Miklos Szeredi]

On Fri, Oct 30, 2020 at 7:42 PM Dmitry Vyukov <dvyukov@google.com> wrote:
>
> On Fri, Oct 30, 2020 at 2:02 PM Miklos Szeredi <miklos@szeredi.hu> wrote:
> >
> > On Mon, Aug 24, 2020 at 11:00 PM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> > >
> > > On Mon, Aug 24, 2020 at 9:37 PM syzbot
> > > <syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com> wrote:
> > > > syzbot has found a reproducer for the following issue on:
> > >
> > > Looping in fsdevel and OverlayFS maintainers, as this seems to be
> > > FS/OverlayFS related...
> >
> > Hmm, the oopsing code is always something like:
> >
> > All code
> > ========
> >    0: 1b fe                sbb    %esi,%edi
> >    2: 49 8d 5e 08          lea    0x8(%r14),%rbx
> >    6: 48 89 d8              mov    %rbx,%rax
> >    9: 48 c1 e8 03          shr    $0x3,%rax
> >    d: 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1)
> >   12: 74 08                je     0x1c
> >   14: 48 89 df              mov    %rbx,%rdi
> >   17: e8 bc b4 5b fe        callq  0xfffffffffe5bb4d8
> >   1c: 48 8b 1b              mov    (%rbx),%rbx
> >   1f: 48 83 c3 68          add    $0x68,%rbx
> >   23: 48 89 d8              mov    %rbx,%rax
> >   26: 48 c1 e8 03          shr    $0x3,%rax
> >   2a:* 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
> >   2f: 74 08                je     0x39
> >   31: 48 89 df              mov    %rbx,%rdi
> >   34: e8 9f b4 5b fe        callq  0xfffffffffe5bb4d8
> >   39: 48 8b 1b              mov    (%rbx),%rbx
> >   3c: 48 83 c3 0c          add    $0xc,%rbx
> >
> >
> > And that looks (to me) like the unrolled loop in call_int_hook().  I
> > don't see how that could be related to overlayfs, though it's
> > definitely interesting why it only triggers from
> > overlay->vfs_getattr()->security_inode_getattr()...
>
>
> >   26: 48 c1 e8 03          shr    $0x3,%rax
> >   2a:* 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
>
>
> This access is part of KASAN check. But the original address kernel
> tries to access is NULL, so it's not an issue with KASAN.
>
> The line is this:
>
> int security_inode_getattr(const struct path *path)
> {
>     if (unlikely(IS_PRIVATE(d_backing_inode(path->dentry))))
>         return 0;
>
> So it's either path is NULL, or something in d_backing_inode
> dereferences NULL path->dentry.
>
> The reproducer does involve overlayfs:
>
> mkdir(&(0x7f0000000240)='./file1\x00', 0x0)
> mkdir(&(0x7f0000000300)='./bus\x00', 0x0)
> r0 = creat(&(0x7f00000000c0)='./bus/file1\x00', 0x0)
> mkdir(&(0x7f0000000080)='./file0\x00', 0x0)
> mount$overlay(0x400002, &(0x7f0000000000)='./bus\x00',
> &(0x7f0000000100)='overlay\x00', 0x0,
> &(0x7f00000003c0)=ANY=[@ANYBLOB='upperdir=./file1,lowerdir=./bus,workdir=./file0,metacopy=on'])
> link(&(0x7f0000000200)='./bus/file1\x00', &(0x7f00000002c0)='./bus/file0\x00')
> write$RDMA_USER_CM_CMD_RESOLVE_ADDR(r0, 0x0, 0x0)
> acct(&(0x7f0000000040)='./bus/file0\x00')
>
> Though, it may be overlayfs-related, or it may be a generic bug that
> requires a tricky reproducer and the only reproducer syzbot come up
> with happened to involve overlayfs.
> But there are 4 reproducers on syzbot dashboard and all of them
> involve overlayfs and they are somewhat different. So my bet would be
> on overlayfs.

Seems there's no C reproducer, though.   Can this be reproduced
without KASAN obfuscating the oops?

Thanks,
Miklos

Re: general protection fault in security_inode_getattr

[Dmitry Vyukov]

On Fri, Oct 30, 2020 at 8:21 PM Miklos Szeredi <miklos@szeredi.hu> wrote:
> > > On Mon, Aug 24, 2020 at 11:00 PM Ondrej Mosnacek <omosnace@redhat.com> wrote:
> > > >
> > > > On Mon, Aug 24, 2020 at 9:37 PM syzbot
> > > > <syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com> wrote:
> > > > > syzbot has found a reproducer for the following issue on:
> > > >
> > > > Looping in fsdevel and OverlayFS maintainers, as this seems to be
> > > > FS/OverlayFS related...
> > >
> > > Hmm, the oopsing code is always something like:
> > >
> > > All code
> > > ========
> > >    0: 1b fe                sbb    %esi,%edi
> > >    2: 49 8d 5e 08          lea    0x8(%r14),%rbx
> > >    6: 48 89 d8              mov    %rbx,%rax
> > >    9: 48 c1 e8 03          shr    $0x3,%rax
> > >    d: 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1)
> > >   12: 74 08                je     0x1c
> > >   14: 48 89 df              mov    %rbx,%rdi
> > >   17: e8 bc b4 5b fe        callq  0xfffffffffe5bb4d8
> > >   1c: 48 8b 1b              mov    (%rbx),%rbx
> > >   1f: 48 83 c3 68          add    $0x68,%rbx
> > >   23: 48 89 d8              mov    %rbx,%rax
> > >   26: 48 c1 e8 03          shr    $0x3,%rax
> > >   2a:* 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
> > >   2f: 74 08                je     0x39
> > >   31: 48 89 df              mov    %rbx,%rdi
> > >   34: e8 9f b4 5b fe        callq  0xfffffffffe5bb4d8
> > >   39: 48 8b 1b              mov    (%rbx),%rbx
> > >   3c: 48 83 c3 0c          add    $0xc,%rbx
> > >
> > >
> > > And that looks (to me) like the unrolled loop in call_int_hook().  I
> > > don't see how that could be related to overlayfs, though it's
> > > definitely interesting why it only triggers from
> > > overlay->vfs_getattr()->security_inode_getattr()...
> >
> >
> > >   26: 48 c1 e8 03          shr    $0x3,%rax
> > >   2a:* 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
> >
> >
> > This access is part of KASAN check. But the original address kernel
> > tries to access is NULL, so it's not an issue with KASAN.
> >
> > The line is this:
> >
> > int security_inode_getattr(const struct path *path)
> > {
> >     if (unlikely(IS_PRIVATE(d_backing_inode(path->dentry))))
> >         return 0;
> >
> > So it's either path is NULL, or something in d_backing_inode
> > dereferences NULL path->dentry.
> >
> > The reproducer does involve overlayfs:
> >
> > mkdir(&(0x7f0000000240)='./file1\x00', 0x0)
> > mkdir(&(0x7f0000000300)='./bus\x00', 0x0)
> > r0 = creat(&(0x7f00000000c0)='./bus/file1\x00', 0x0)
> > mkdir(&(0x7f0000000080)='./file0\x00', 0x0)
> > mount$overlay(0x400002, &(0x7f0000000000)='./bus\x00',
> > &(0x7f0000000100)='overlay\x00', 0x0,
> > &(0x7f00000003c0)=ANY=[@ANYBLOB='upperdir=./file1,lowerdir=./bus,workdir=./file0,metacopy=on'])
> > link(&(0x7f0000000200)='./bus/file1\x00', &(0x7f00000002c0)='./bus/file0\x00')
> > write$RDMA_USER_CM_CMD_RESOLVE_ADDR(r0, 0x0, 0x0)
> > acct(&(0x7f0000000040)='./bus/file0\x00')
> >
> > Though, it may be overlayfs-related, or it may be a generic bug that
> > requires a tricky reproducer and the only reproducer syzbot come up
> > with happened to involve overlayfs.
> > But there are 4 reproducers on syzbot dashboard and all of them
> > involve overlayfs and they are somewhat different. So my bet would be
> > on overlayfs.
>
> Seems there's no C reproducer, though.   Can this be reproduced
> without KASAN obfuscating the oops?

I guess so.
If you are interest in what exact field is NULL, I think there is
enough info in the asm already:

> > >    2: 49 8d 5e 08          lea    0x8(%r14),%rbx
> > >    6: 48 89 d8              mov    %rbx,%rax
> > >    9: 48 c1 e8 03          shr    $0x3,%rax
> > >    d: 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1)
> > >   12: 74 08                je     0x1c
> > >   14: 48 89 df              mov    %rbx,%rdi
> > >   17: e8 bc b4 5b fe        callq  0xfffffffffe5bb4d8
> > >   1c: 48 8b 1b              mov    (%rbx),%rbx
> > >   1f: 48 83 c3 68          add    $0x68,%rbx
> > >   23: 48 89 d8              mov    %rbx,%rax
> > >   26: 48 c1 e8 03          shr    $0x3,%rax
> > >   2a:* 42 80 3c 38 00        cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction

The access via the NULL pointer happens with offset 0x68:

> > >   1f: 48 83 c3 68          add    $0x68,%rbx

So we just need to find what's here accesses with offset 0x68:

> >     if (unlikely(IS_PRIVATE(d_backing_inode(path->dentry))))

And that pointer itself was loaded from something at offset 0x8 previously:

> > >    2: 49 8d 5e 08          lea    0x8(%r14),%rbx

Re: general protection fault in security_inode_getattr

[syzbot]

syzbot has bisected this issue to:

commit 35697c12d7ffd31a56d3c9604066a166b75d0169
Author: Yonghong Song <yhs@fb.com>
Date:   Thu Jan 16 17:40:04 2020 +0000

    selftests/bpf: Fix test_progs send_signal flakiness with nmi mode

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13032139900000
start commit:   d012a719 Linux 5.9-rc2
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=10832139900000
console output: https://syzkaller.appspot.com/x/log.txt?x=17032139900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=891ca5711a9f1650
dashboard link: https://syzkaller.appspot.com/bug?extid=f07cc9be8d1d226947ed
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=104a650e900000

Reported-by: syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com
Fixes: 35697c12d7ff ("selftests/bpf: Fix test_progs send_signal flakiness with nmi mode")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: general protection fault in security_inode_getattr

[Yonghong Song]

On 8/24/20 5:32 PM, syzbot wrote:
> syzbot has bisected this issue to:
> 
> commit 35697c12d7ffd31a56d3c9604066a166b75d0169
> Author: Yonghong Song <yhs@fb.com>
> Date:   Thu Jan 16 17:40:04 2020 +0000
> 
>      selftests/bpf: Fix test_progs send_signal flakiness with nmi mode

The above patch changed file:
     tools/testing/selftests/bpf/prog_tests/send_signal.c
It is unlikely it caused the issue.

> 
> bisection log:  https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_bisect.txt-3Fx-3D13032139900000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=854z77F3pbTpgGUCFUwM1OSEUj4NbiNIZsaad0Xg4qc&s=Le6D_jfzkec28_qNhbUwMesaUeBGaKEG6RLN3ZCzE1s&e=
> start commit:   d012a719 Linux 5.9-rc2
> git tree:       upstream
> final oops:     https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_report.txt-3Fx-3D10832139900000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=854z77F3pbTpgGUCFUwM1OSEUj4NbiNIZsaad0Xg4qc&s=VbLXb22TgxAtiPQTEq0t5r0WgNDiFwstWKnme0tWBLE&e=
> console output: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_log.txt-3Fx-3D17032139900000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=854z77F3pbTpgGUCFUwM1OSEUj4NbiNIZsaad0Xg4qc&s=yu72HnqjHzOTtJ5dyD7q0QW9sOwEO6pPHjeYTTutKdc&e=
> kernel config:  https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_.config-3Fx-3D891ca5711a9f1650&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=854z77F3pbTpgGUCFUwM1OSEUj4NbiNIZsaad0Xg4qc&s=6cylIRBZjHQmgkJQoofuLN2XSifb-13qrrj58PQpBYs&e=
> dashboard link: https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_bug-3Fextid-3Df07cc9be8d1d226947ed&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=854z77F3pbTpgGUCFUwM1OSEUj4NbiNIZsaad0Xg4qc&s=siCrm2aO-fzR3Nym_zaPQQnmxMlJo0bRj87zgm7o5mY&e=
> syz repro:      https://urldefense.proofpoint.com/v2/url?u=https-3A__syzkaller.appspot.com_x_repro.syz-3Fx-3D104a650e900000&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=854z77F3pbTpgGUCFUwM1OSEUj4NbiNIZsaad0Xg4qc&s=yNEvyRe2bO4AKgq2UuJc32katp4k4UGKwMUDEBlhM7E&e=
> 
> Reported-by: syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com
> Fixes: 35697c12d7ff ("selftests/bpf: Fix test_progs send_signal flakiness with nmi mode")
> 
> For information about bisection process see: https://urldefense.proofpoint.com/v2/url?u=https-3A__goo.gl_tpsmEJ-23bisection&d=DwIBaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=854z77F3pbTpgGUCFUwM1OSEUj4NbiNIZsaad0Xg4qc&s=K4KdZK8rBgxDv4M9uwEndkCB4mCatTH-opwefN-0b-M&e=
> 

Re: [syzbot] general protection fault in security_inode_getattr

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    55be6084c8e0 Merge tag 'timers-core-2022-10-05' of git://g..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=147637c6880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=df75278aabf0681a
dashboard link: https://syzkaller.appspot.com/bug?extid=f07cc9be8d1d226947ed
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1585a0c2880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1480a464880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6c791937c012/disk-55be6084.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cb21a2879b4c/vmlinux-55be6084.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2d56267ed26f/mount_1.gz

The issue was bisected to:

commit 35697c12d7ffd31a56d3c9604066a166b75d0169
Author: Yonghong Song <yhs@fb.com>
Date:   Thu Jan 16 17:40:04 2020 +0000

    selftests/bpf: Fix test_progs send_signal flakiness with nmi mode

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13032139900000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=10832139900000
console output: https://syzkaller.appspot.com/x/log.txt?x=17032139900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com
Fixes: 35697c12d7ff ("selftests/bpf: Fix test_progs send_signal flakiness with nmi mode")

general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 0 PID: 3761 Comm: syz-executor352 Not tainted 6.0.0-syzkaller-09589-g55be6084c8e0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
RIP: 0010:d_backing_inode include/linux/dcache.h:542 [inline]
RIP: 0010:security_inode_getattr+0x46/0x140 security/security.c:1345
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 04 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5d 08 48 8d 7b 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d7 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc9000400f578 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000000d RSI: ffffffff83bd72fe RDI: 0000000000000068
RBP: ffffc9000400f750 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 000000000008c07d R12: ffff8880763dca48
R13: ffffc9000400f750 R14: 00000000000007ff R15: 0000000000000000
FS:  00007f246f27e700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f246f27e718 CR3: 00000000717a9000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 vfs_getattr+0x22/0x60 fs/stat.c:158
 ovl_copy_up_one+0x12c/0x2870 fs/overlayfs/copy_up.c:965
 ovl_copy_up_flags+0x150/0x1d0 fs/overlayfs/copy_up.c:1047
 ovl_maybe_copy_up+0x140/0x190 fs/overlayfs/copy_up.c:1079
 ovl_open+0xf1/0x2d0 fs/overlayfs/file.c:152
 do_dentry_open+0x6cc/0x13f0 fs/open.c:882
 do_open fs/namei.c:3557 [inline]
 path_openat+0x1c92/0x28f0 fs/namei.c:3691
 do_filp_open+0x1b6/0x400 fs/namei.c:3718
 do_sys_openat2+0x16d/0x4c0 fs/open.c:1310
 do_sys_open fs/open.c:1326 [inline]
 __do_sys_open fs/open.c:1334 [inline]
 __se_sys_open fs/open.c:1330 [inline]
 __x64_sys_open+0x119/0x1c0 fs/open.c:1330
 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: 0033:0x7f246f2f2b49
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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:00007f246f27e2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007f246f3774b0 RCX: 00007f246f2f2b49
RDX: 0000000000000000 RSI: 0000000000000300 RDI: 0000000020000140
RBP: 00007f246f3442ac R08: 00007f246f27e700 R09: 0000000000000000
R10: 00007f246f27e700 R11: 0000000000000246 R12: 0031656c69662f2e
R13: 79706f636174656d R14: 0079616c7265766f R15: 00007f246f3774b8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:d_backing_inode include/linux/dcache.h:542 [inline]
RIP: 0010:security_inode_getattr+0x46/0x140 security/security.c:1345
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 04 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5d 08 48 8d 7b 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d7 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc9000400f578 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000000000d RSI: ffffffff83bd72fe RDI: 0000000000000068
RBP: ffffc9000400f750 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 000000000008c07d R12: ffff8880763dca48
R13: ffffc9000400f750 R14: 00000000000007ff R15: 0000000000000000
FS:  00007f246f27e700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005643c9471000 CR3: 00000000717a9000 CR4: 0000000000350ee0
----------------
Code disassembly (best guess):
   0:	48 89 fa             	mov    %rdi,%rdx
   3:	48 c1 ea 03          	shr    $0x3,%rdx
   7:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   b:	0f 85 04 01 00 00    	jne    0x115
  11:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  18:	fc ff df
  1b:	49 8b 5d 08          	mov    0x8(%r13),%rbx
  1f:	48 8d 7b 68          	lea    0x68(%rbx),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 d7 00 00 00    	jne    0x10b
  34:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  3b:	fc ff df
  3e:	48                   	rex.W
  3f:	8b                   	.byte 0x8b

Re: [syzbot] general protection fault in security_inode_getattr

[Paul Moore]

On Sat, Oct 15, 2022 at 1:24 PM syzbot
<syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    55be6084c8e0 Merge tag 'timers-core-2022-10-05' of git://g..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=147637c6880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=df75278aabf0681a
> dashboard link: https://syzkaller.appspot.com/bug?extid=f07cc9be8d1d226947ed
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1585a0c2880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1480a464880000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/6c791937c012/disk-55be6084.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cb21a2879b4c/vmlinux-55be6084.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/2d56267ed26f/mount_1.gz
>
> The issue was bisected to:
>
> commit 35697c12d7ffd31a56d3c9604066a166b75d0169
> Author: Yonghong Song <yhs@fb.com>
> Date:   Thu Jan 16 17:40:04 2020 +0000
>
>     selftests/bpf: Fix test_progs send_signal flakiness with nmi mode
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13032139900000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=10832139900000
> console output: https://syzkaller.appspot.com/x/log.txt?x=17032139900000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com
> Fixes: 35697c12d7ff ("selftests/bpf: Fix test_progs send_signal flakiness with nmi mode")
>
> general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
> CPU: 0 PID: 3761 Comm: syz-executor352 Not tainted 6.0.0-syzkaller-09589-g55be6084c8e0 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> RIP: 0010:d_backing_inode include/linux/dcache.h:542 [inline]
> RIP: 0010:security_inode_getattr+0x46/0x140 security/security.c:1345
> Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 04 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5d 08 48 8d 7b 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d7 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
> RSP: 0018:ffffc9000400f578 EFLAGS: 00010212
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 000000000000000d RSI: ffffffff83bd72fe RDI: 0000000000000068
> RBP: ffffc9000400f750 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 000000000008c07d R12: ffff8880763dca48
> R13: ffffc9000400f750 R14: 00000000000007ff R15: 0000000000000000
> FS:  00007f246f27e700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f246f27e718 CR3: 00000000717a9000 CR4: 0000000000350ef0
> Call Trace:
>  <TASK>
>  vfs_getattr+0x22/0x60 fs/stat.c:158
>  ovl_copy_up_one+0x12c/0x2870 fs/overlayfs/copy_up.c:965
>  ovl_copy_up_flags+0x150/0x1d0 fs/overlayfs/copy_up.c:1047
>  ovl_maybe_copy_up+0x140/0x190 fs/overlayfs/copy_up.c:1079
>  ovl_open+0xf1/0x2d0 fs/overlayfs/file.c:152
>  do_dentry_open+0x6cc/0x13f0 fs/open.c:882
>  do_open fs/namei.c:3557 [inline]
>  path_openat+0x1c92/0x28f0 fs/namei.c:3691
>  do_filp_open+0x1b6/0x400 fs/namei.c:3718
>  do_sys_openat2+0x16d/0x4c0 fs/open.c:1310
>  do_sys_open fs/open.c:1326 [inline]
>  __do_sys_open fs/open.c:1334 [inline]
>  __se_sys_open fs/open.c:1330 [inline]
>  __x64_sys_open+0x119/0x1c0 fs/open.c:1330
>  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: 0033:0x7f246f2f2b49
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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:00007f246f27e2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
> RAX: ffffffffffffffda RBX: 00007f246f3774b0 RCX: 00007f246f2f2b49
> RDX: 0000000000000000 RSI: 0000000000000300 RDI: 0000000020000140
> RBP: 00007f246f3442ac R08: 00007f246f27e700 R09: 0000000000000000
> R10: 00007f246f27e700 R11: 0000000000000246 R12: 0031656c69662f2e
> R13: 79706f636174656d R14: 0079616c7265766f R15: 00007f246f3774b8
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---

It doesn't look like this is a problem with
security_inode_getattr()/d_backing_inode() as it appears that the
passed path struct pointer has a bogus/NULL path->dentry pointer and
to the best of my knowledge it would appear that vfs_getattr() (the
caller) requires a valid path->dentry value.

Looking quickly at the code, I wonder if there is something wonky
going on in the overlayfs code, specifically ovl_copy_up_flags() and
ovl_copy_up_one() as they have to play a number of tricks to handle
the transparent overlays and copy up operations.  I'm not an overlayfs
expert, but that seems like a good place to start digging further into
this.

-- 
paul-moore.com

Re: [syzbot] general protection fault in security_inode_getattr

[Tetsuo Handa]

On 2022/10/16 23:52, Paul Moore wrote:
> It doesn't look like this is a problem with
> security_inode_getattr()/d_backing_inode() as it appears that the
> passed path struct pointer has a bogus/NULL path->dentry pointer and
> to the best of my knowledge it would appear that vfs_getattr() (the
> caller) requires a valid path->dentry value.
> 
> Looking quickly at the code, I wonder if there is something wonky
> going on in the overlayfs code, specifically ovl_copy_up_flags() and
> ovl_copy_up_one() as they have to play a number of tricks to handle
> the transparent overlays and copy up operations.  I'm not an overlayfs
> expert, but that seems like a good place to start digging further into
> this.

Right. This is a bug in overlayfs code. Probably due to some race condition,
ovl_copy_up_flags() is calling ovl_copy_up_one() with "next" dentry with
"struct ovl_entry"->numlower == 0. As a result, ovl_path_lower() from
ovl_copy_up_one() fills ctx.lowerpath with NULLs, and vfs_getattr() gets
surprised by ctx.lowerpath.dentry == NULL.

If we can't avoid selecting a dentry with "struct ovl_entry"->numlower == 0 using
some lock, I guess that we would need to use a workaround suggested by Hillf Danton
at https://groups.google.com/g/syzkaller-bugs/c/xDcxFKSppfE/m/b38Tv7LoAAAJ .

Re: [syzbot] general protection fault in security_inode_getattr

[Yonghong Song]

On 10/15/22 10:24 AM, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    55be6084c8e0 Merge tag 'timers-core-2022-10-05' of git://g..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=147637c6880000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=df75278aabf0681a
> dashboard link: https://syzkaller.appspot.com/bug?extid=f07cc9be8d1d226947ed
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1585a0c2880000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1480a464880000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/6c791937c012/disk-55be6084.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cb21a2879b4c/vmlinux-55be6084.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/2d56267ed26f/mount_1.gz
> 
> The issue was bisected to:
> 
> commit 35697c12d7ffd31a56d3c9604066a166b75d0169
> Author: Yonghong Song <yhs@fb.com>
> Date:   Thu Jan 16 17:40:04 2020 +0000
> 
>      selftests/bpf: Fix test_progs send_signal flakiness with nmi mode

It cannot be this patch as it tried to modify a bpf selftest and it
should not impact the kernel.

> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=13032139900000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=10832139900000
> console output: https://syzkaller.appspot.com/x/log.txt?x=17032139900000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+f07cc9be8d1d226947ed@syzkaller.appspotmail.com
> Fixes: 35697c12d7ff ("selftests/bpf: Fix test_progs send_signal flakiness with nmi mode")
> 
> general protection fault, probably for non-canonical address 0xdffffc000000000d: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
> CPU: 0 PID: 3761 Comm: syz-executor352 Not tainted 6.0.0-syzkaller-09589-g55be6084c8e0 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
> RIP: 0010:d_backing_inode include/linux/dcache.h:542 [inline]
> RIP: 0010:security_inode_getattr+0x46/0x140 security/security.c:1345
> Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 04 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5d 08 48 8d 7b 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d7 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
> RSP: 0018:ffffc9000400f578 EFLAGS: 00010212
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 000000000000000d RSI: ffffffff83bd72fe RDI: 0000000000000068
> RBP: ffffc9000400f750 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 000000000008c07d R12: ffff8880763dca48
> R13: ffffc9000400f750 R14: 00000000000007ff R15: 0000000000000000
> FS:  00007f246f27e700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f246f27e718 CR3: 00000000717a9000 CR4: 0000000000350ef0
> Call Trace:
>   <TASK>
>   vfs_getattr+0x22/0x60 fs/stat.c:158
>   ovl_copy_up_one+0x12c/0x2870 fs/overlayfs/copy_up.c:965
>   ovl_copy_up_flags+0x150/0x1d0 fs/overlayfs/copy_up.c:1047
>   ovl_maybe_copy_up+0x140/0x190 fs/overlayfs/copy_up.c:1079
>   ovl_open+0xf1/0x2d0 fs/overlayfs/file.c:152
>   do_dentry_open+0x6cc/0x13f0 fs/open.c:882
>   do_open fs/namei.c:3557 [inline]
>   path_openat+0x1c92/0x28f0 fs/namei.c:3691
>   do_filp_open+0x1b6/0x400 fs/namei.c:3718
>   do_sys_openat2+0x16d/0x4c0 fs/open.c:1310
>   do_sys_open fs/open.c:1326 [inline]
>   __do_sys_open fs/open.c:1334 [inline]
>   __se_sys_open fs/open.c:1330 [inline]
>   __x64_sys_open+0x119/0x1c0 fs/open.c:1330
>   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: 0033:0x7f246f2f2b49
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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:00007f246f27e2f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
> RAX: ffffffffffffffda RBX: 00007f246f3774b0 RCX: 00007f246f2f2b49
> RDX: 0000000000000000 RSI: 0000000000000300 RDI: 0000000020000140
> RBP: 00007f246f3442ac R08: 00007f246f27e700 R09: 0000000000000000
> R10: 00007f246f27e700 R11: 0000000000000246 R12: 0031656c69662f2e
> R13: 79706f636174656d R14: 0079616c7265766f R15: 00007f246f3774b8
>   </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:d_backing_inode include/linux/dcache.h:542 [inline]
> RIP: 0010:security_inode_getattr+0x46/0x140 security/security.c:1345
> Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 04 01 00 00 48 b8 00 00 00 00 00 fc ff df 49 8b 5d 08 48 8d 7b 68 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 d7 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
> RSP: 0018:ffffc9000400f578 EFLAGS: 00010212
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 000000000000000d RSI: ffffffff83bd72fe RDI: 0000000000000068
> RBP: ffffc9000400f750 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 000000000008c07d R12: ffff8880763dca48
> R13: ffffc9000400f750 R14: 00000000000007ff R15: 0000000000000000
> FS:  00007f246f27e700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00005643c9471000 CR3: 00000000717a9000 CR4: 0000000000350ee0
> ----------------
> Code disassembly (best guess):
>     0:	48 89 fa             	mov    %rdi,%rdx
>     3:	48 c1 ea 03          	shr    $0x3,%rdx
>     7:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
>     b:	0f 85 04 01 00 00    	jne    0x115
>    11:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
>    18:	fc ff df
>    1b:	49 8b 5d 08          	mov    0x8(%r13),%rbx
>    1f:	48 8d 7b 68          	lea    0x68(%rbx),%rdi
>    23:	48 89 fa             	mov    %rdi,%rdx
>    26:	48 c1 ea 03          	shr    $0x3,%rdx
> * 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
>    2e:	0f 85 d7 00 00 00    	jne    0x10b
>    34:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
>    3b:	fc ff df
>    3e:	48                   	rex.W
>    3f:	8b                   	.byte 0x8b
>