Re: [syzbot] [mm?] general protection fault in mremap

[Aleksandr Nogikh <nogikh@google.com>]

Hi Lorenzo,

Thanks for looking at the report!

On Mon, Apr 7, 2025 at 12:09 PM 'Lorenzo Stoakes' via syzkaller-bugs
<syzkaller-bugs@googlegroups.com> wrote:
>
> I did actually try to mark this fixed, but apparently syz fix doesn't work or
> doesn't prevent other syzbots from duplicating reports.

This part is not very clear - why would #syz fix: title not work well here?

>
> Anyway, this is fixed in commit 36eed5400805 ("mm/mremap: do not set
> vrm->vma NULL immediately prior to checking it"), was fixed a long time
> ago, as soon as reported, and it's been a matter of waiting for this to
> land in Linus's tree.
>
> This is now fixed, upstream, and this report is - as a result - redundant.
>
> Thanks, Lorenzo

-- 
Aleksandr

>
> On Sat, Apr 05, 2025 at 05:16:31PM -0700, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    a2cc6ff5ec8f Merge tag 'firewire-updates-6.15' of git://gi..
> > git tree:       upstream
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=11ab27cf980000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=adffebefc9feb9d6
> > dashboard link: https://syzkaller.appspot.com/bug?extid=5250c4727db03e3436cc
> > compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1693d404580000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=178ac94c580000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/8ecd2318067e/disk-a2cc6ff5.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/05691b82062c/vmlinux-a2cc6ff5.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/4698994e99d4/bzImage-a2cc6ff5.xz
> >
> > The issue was bisected to:
> >
> > commit d5c8aec0542e2d79b64de9089b88fabdebe05c1e
> > Author: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> > Date:   Mon Mar 10 20:50:37 2025 +0000
> >
> >     mm/mremap: initial refactor of move_vma()
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11ff2a74580000
> > final oops:     https://syzkaller.appspot.com/x/report.txt?x=13ff2a74580000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15ff2a74580000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+5250c4727db03e3436cc@syzkaller.appspotmail.com
> > Fixes: d5c8aec0542e ("mm/mremap: initial refactor of move_vma()")
> >
> > Code: 48 83 c4 28 c3 e8 17 1a 00 00 0f 1f 80 00 00 00 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:00007fff0b8738c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
> > RAX: ffffffffffffffda RBX: 00007fff0b8738d0 RCX: 00007f46ffb182e9
> > RDX: 0000000000003000 RSI: 0000000000001000 RDI: 0000200000ffc000
> > RBP: 0000000000000001 R08: 0000200000ffa000 R09: 00007f46ffb80031
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f46ffb83618
> > R13: 00007fff0b873aa8 R14: 0000000000000001 R15: 0000000000000001
> >  </TASK>
> > Oops: general protection fault, probably for non-canonical address 0xdffffc0000000004: 0000 [#1] SMP KASAN NOPTI
> > KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
> > CPU: 0 UID: 0 PID: 5820 Comm: syz-executor115 Not tainted 6.14.0-syzkaller-12966-ga2cc6ff5ec8f #0 PREEMPT(full)
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
> > RIP: 0010:vrm_uncharge mm/mremap.c:964 [inline]
> > RIP: 0010:expand_vma_in_place mm/mremap.c:1566 [inline]
> > RIP: 0010:expand_vma mm/mremap.c:1621 [inline]
> > RIP: 0010:mremap_at mm/mremap.c:1682 [inline]
> > RIP: 0010:do_mremap mm/mremap.c:1727 [inline]
> > RIP: 0010:__do_sys_mremap+0x1392/0x15c0 mm/mremap.c:1784
> > Code: 0f 85 45 02 00 00 48 8b 04 24 c6 84 24 70 01 00 00 01 48 01 85 68 02 00 00 eb 9a e8 18 34 af ff 48 b8 04 00 00 00 00 fc ff df <80> 38 00 0f 85 a7 01 00 00 48 8b 2c 25 20 00 00 00 31 ff 81 e5 00
> > RSP: 0018:ffffc900039dfd20 EFLAGS: 00010293
> > RAX: dffffc0000000004 RBX: ffff88802b765a00 RCX: ffffffff821183c6
> > RDX: ffff88805c7b8000 RSI: ffffffff820c0cb8 RDI: 0000000000000005
> > RBP: ffff8880341fb780 R08: 0000000000000005 R09: 0000000000000000
> > R10: 00000000fffffff4 R11: 0000000000000001 R12: 0000000000002000
> > R13: 1ffff9200073bfaa R14: 0000200000ffc000 R15: ffff88802b765b70
> > FS:  00005555814db380(0000) GS:ffff8881249b8000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fff0b8728e0 CR3: 000000007802e000 CR4: 00000000003526f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  <TASK>
> >  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> >  do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94
> >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7f46ffb182e9
> > Code: 48 83 c4 28 c3 e8 17 1a 00 00 0f 1f 80 00 00 00 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:00007fff0b8738c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
> > RAX: ffffffffffffffda RBX: 00007fff0b8738d0 RCX: 00007f46ffb182e9
> > RDX: 0000000000003000 RSI: 0000000000001000 RDI: 0000200000ffc000
> > RBP: 0000000000000001 R08: 0000200000ffa000 R09: 00007f46ffb80031
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f46ffb83618
> > R13: 00007fff0b873aa8 R14: 0000000000000001 R15: 0000000000000001
> >  </TASK>
> > Modules linked in:
> > ---[ end trace 0000000000000000 ]---
> > RIP: 0010:vrm_uncharge mm/mremap.c:964 [inline]
> > RIP: 0010:expand_vma_in_place mm/mremap.c:1566 [inline]
> > RIP: 0010:expand_vma mm/mremap.c:1621 [inline]
> > RIP: 0010:mremap_at mm/mremap.c:1682 [inline]
> > RIP: 0010:do_mremap mm/mremap.c:1727 [inline]
> > RIP: 0010:__do_sys_mremap+0x1392/0x15c0 mm/mremap.c:1784
> > Code: 0f 85 45 02 00 00 48 8b 04 24 c6 84 24 70 01 00 00 01 48 01 85 68 02 00 00 eb 9a e8 18 34 af ff 48 b8 04 00 00 00 00 fc ff df <80> 38 00 0f 85 a7 01 00 00 48 8b 2c 25 20 00 00 00 31 ff 81 e5 00
> > RSP: 0018:ffffc900039dfd20 EFLAGS: 00010293
> > RAX: dffffc0000000004 RBX: ffff88802b765a00 RCX: ffffffff821183c6
> > RDX: ffff88805c7b8000 RSI: ffffffff820c0cb8 RDI: 0000000000000005
> > RBP: ffff8880341fb780 R08: 0000000000000005 R09: 0000000000000000
> > R10: 00000000fffffff4 R11: 0000000000000001 R12: 0000000000002000
> > R13: 1ffff9200073bfaa R14: 0000200000ffc000 R15: ffff88802b765b70
> > FS:  00005555814db380(0000) GS:ffff8881249b8000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fff0b8728e0 CR3: 000000007802e000 CR4: 00000000003526f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > ----------------
> > Code disassembly (best guess):
> >    0: 48 83 c4 28             add    $0x28,%rsp
> >    4: c3                      ret
> >    5: e8 17 1a 00 00          call   0x1a21
> >    a: 0f 1f 80 00 00 00 00    nopl   0x0(%rax)
> >   11: 48 89 f8                mov    %rdi,%rax
> >   14: 48 89 f7                mov    %rsi,%rdi
> >   17: 48 89 d6                mov    %rdx,%rsi
> >   1a: 48 89 ca                mov    %rcx,%rdx
> >   1d: 4d 89 c2                mov    %r8,%r10
> >   20: 4d 89 c8                mov    %r9,%r8
> >   23: 4c 8b 4c 24 08          mov    0x8(%rsp),%r9
> >   28: 0f 05                   syscall
> > * 2a: 48 3d 01 f0 ff ff       cmp    $0xfffffffffffff001,%rax <-- trapping instruction
> >   30: 73 01                   jae    0x33
> >   32: c3                      ret
> >   33: 48 c7 c1 b8 ff ff ff    mov    $0xffffffffffffffb8,%rcx
> >   3a: f7 d8                   neg    %eax
> >   3c: 64 89 01                mov    %eax,%fs:(%rcx)
> >   3f: 48                      rex.W
> >
> >
> > ---
> > 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@googlegroups.com.
> >
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> >
> > If the report is already addressed, let syzbot know by replying with:
> > #syz fix: exact-commit-title
> >
> > If you want syzbot to run the reproducer, reply with:
> > #syz test: git://repo/address.git branch-or-commit-hash
> > If you attach or paste a git patch, syzbot will apply it before testing.
> >
> > If you want to overwrite report's subsystems, reply with:
> > #syz set subsystems: new-subsystem
> > (See the list of subsystem names on the web dashboard)
> >
> > If the report is a duplicate of another one, reply with:
> > #syz dup: exact-subject-of-another-report
> >
> > If you want to undo deduplication, reply with:
> > #syz undup
>
> --