Re: [syzbot] [overlayfs?] general protection fault in do_dentry_open

On Thu, Mar 19, 2026 at 8:20 AM syzbot
<[email protected]> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    8e5a478b6d6a Add linux-next specific files for 20260317
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=1391d602580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1d7d59e3bf573a4f
> dashboard link: https://syzkaller.appspot.com/bug?extid=f34aab278bf5d664e2be
> compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15395b4a580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=130ef8da580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d3f80068a490/disk-8e5a478b.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/5bfbdf243860/vmlinux-8e5a478b.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/f43f1bae2625/bzImage-8e5a478b.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
> CPU: 0 UID: 0 PID: 6035 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
> RIP: 0010:do_dentry_open+0xaf/0x14e0 fs/open.c:896
> Code: 44 24 28 80 3c 28 00 74 08 4c 89 ff e8 fa 5e ef ff 4c 89 7c 24 20 4d 89 27 4d 8d 7c 24 30 4c 89 f8 48 c1 e8 03 48 89 44 24 58 <80> 3c 28 00 74 08 4c 89 ff e8 e3 5d ef ff 4c 89 7c 24 60 4d 8b 3f
> RSP: 0018:ffffc900037d7638 EFLAGS: 00010206
> RAX: 0000000000000006 RBX: ffff88807217db60 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000004 RDI: 00000000ffffffff
> RBP: dffffc0000000000 R08: ffff88807b54d9b3 R09: 1ffff1100f6a9b36
> R10: dffffc0000000000 R11: ffffed100f6a9b37 R12: 0000000000000000
> R13: 1ffff1100e42fb7d R14: ffff88807217dbe8 R15: 0000000000000030
> FS:  00005555907f6500(0000) GS:ffff888124de1000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000200000001000 CR3: 00000000772e8000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  vfs_open+0x3b/0x340 fs/open.c:1081
>  backing_file_open_user_path+0x24/0x50 fs/file_table.c:73
>  backing_tmpfile_open+0x9b/0xf0 fs/backing-file.c:71
>  ovl_create_tmpfile fs/overlayfs/dir.c:1392 [inline]
>  ovl_tmpfile+0x400/0x810 fs/overlayfs/dir.c:1449
>  vfs_tmpfile+0x3ff/0x890 fs/namei.c:4744
>  do_tmpfile+0xd3/0x240 fs/namei.c:4809
>  path_openat+0x300d/0x3860 fs/namei.c:4843
>  do_file_open+0x23e/0x4a0 fs/namei.c:4881
>  do_sys_openat2+0x113/0x200 fs/open.c:1366
>  do_sys_open fs/open.c:1372 [inline]
>  __do_sys_open fs/open.c:1380 [inline]
>  __se_sys_open fs/open.c:1376 [inline]
>  __x64_sys_open+0x11e/0x150 fs/open.c:1376
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7ff99279c799
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 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 e8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fff78638ef8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
> RAX: ffffffffffffffda RBX: 00007ff992a15fa0 RCX: 00007ff99279c799
> RDX: 0000000000000028 RSI: 0000000000551083 RDI: 0000200000000040
> RBP: 00007ff992832c99 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ff992a15fac R14: 00007ff992a15fa0 R15: 00007ff992a15fa0
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:do_dentry_open+0xaf/0x14e0 fs/open.c:896
> Code: 44 24 28 80 3c 28 00 74 08 4c 89 ff e8 fa 5e ef ff 4c 89 7c 24 20 4d 89 27 4d 8d 7c 24 30 4c 89 f8 48 c1 e8 03 48 89 44 24 58 <80> 3c 28 00 74 08 4c 89 ff e8 e3 5d ef ff 4c 89 7c 24 60 4d 8b 3f
> RSP: 0018:ffffc900037d7638 EFLAGS: 00010206
> RAX: 0000000000000006 RBX: ffff88807217db60 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000004 RDI: 00000000ffffffff
> RBP: dffffc0000000000 R08: ffff88807b54d9b3 R09: 1ffff1100f6a9b36
> R10: dffffc0000000000 R11: ffffed100f6a9b37 R12: 0000000000000000
> R13: 1ffff1100e42fb7d R14: ffff88807217dbe8 R15: 0000000000000030
> FS:  00005555907f6500(0000) GS:ffff888124de1000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000200000001000 CR3: 00000000772e8000 CR4: 00000000003526f0
> ----------------
> Code disassembly (best guess):
>    0:   44 24 28                rex.R and $0x28,%al
>    3:   80 3c 28 00             cmpb   $0x0,(%rax,%rbp,1)
>    7:   74 08                   je     0x11
>    9:   4c 89 ff                mov    %r15,%rdi
>    c:   e8 fa 5e ef ff          call   0xffef5f0b
>   11:   4c 89 7c 24 20          mov    %r15,0x20(%rsp)
>   16:   4d 89 27                mov    %r12,(%r15)
>   19:   4d 8d 7c 24 30          lea    0x30(%r12),%r15
>   1e:   4c 89 f8                mov    %r15,%rax
>   21:   48 c1 e8 03             shr    $0x3,%rax
>   25:   48 89 44 24 58          mov    %rax,0x58(%rsp)
> * 2a:   80 3c 28 00             cmpb   $0x0,(%rax,%rbp,1) <-- trapping instruction
>   2e:   74 08                   je     0x38
>   30:   4c 89 ff                mov    %r15,%rdi
>   33:   e8 e3 5d ef ff          call   0xffef5e1b
>   38:   4c 89 7c 24 60          mov    %r15,0x60(%rsp)
>   3d:   4d 8b 3f                mov    (%r15),%r15
>
>
> ---
> This report is generated by a bot. It may contain errors.
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> syzbot engineers can be reached at [email protected].
>
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>
> 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.

#syz test: https://github.com/amir73il/linux.git vfs-fixes