Forwarded: Re: [syzbot] [exfat?] general protection fault in exfat_utf16_to_nls

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Subject: Re: [syzbot] [exfat?] general protection fault in exfat_utf16_to_nls
Author: ekffu200098@gmail.com

#syz test

On Thu, Sep 25, 2025 at 7:04 AM syzbot
<syzbot+3e9cb93e3c5f90d28e19@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    b5a4da2c459f Add linux-next specific files for 20250924
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15ffad34580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=fc64d939cce41d2
> dashboard link: https://syzkaller.appspot.com/bug?extid=3e9cb93e3c5f90d28e19
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1704cf12580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15c8d4e2580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/127c931e6696/disk-b5a4da2c.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cf4957abd39e/vmlinux-b5a4da2c.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/860d3ac61bac/bzImage-b5a4da2c.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/9006b1673f9f/mount_0.gz
>   fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=11c8d4e2580000)
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3e9cb93e3c5f90d28e19@syzkaller.appspotmail.com
>
> Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] SMP KASAN PTI
> KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
> CPU: 1 UID: 0 PID: 5979 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
> RIP: 0010:exfat_convert_ucs2_to_char fs/exfat/nls.c:441 [inline]
> RIP: 0010:__exfat_utf16_to_nls fs/exfat/nls.c:554 [inline]
> RIP: 0010:exfat_utf16_to_nls+0x21c/0x840 fs/exfat/nls.c:638
> Code: 2e 29 ff 66 41 83 fc 7f 77 14 e8 7f 2a 29 ff e9 b6 00 00 00 e8 75 2a 29 ff e9 a9 00 00 00 48 8b 4c 24 40 48 89 c8 48 c1 e8 03 <42> 80 3c 38 00 74 0f 48 8b 7c 24 40 e8 d3 6b 8e ff 48 8b 4c 24 40
> RSP: 0018:ffffc90003fef760 EFLAGS: 00010202
> RAX: 0000000000000002 RBX: 0000000000000004 RCX: 0000000000000010
> RDX: ffff88802f18bc80 RSI: 00000000000000e1 RDI: 0000000000000080
> RBP: ffffc90003fef850 R08: 0000000000000005 R09: 0000000000000000
> R10: ffffc90003fef7e0 R11: fffff520007fdefc R12: 00000000000000e1
> R13: ffffc90003fefa48 R14: 0000000000000000 R15: dffffc0000000000
> FS:  000055557b9c2500(0000) GS:ffff888125b03000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055557b9e5608 CR3: 00000000734c8000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  exfat_readdir fs/exfat/dir.c:143 [inline]
>  exfat_iterate+0x19a7/0x2050 fs/exfat/dir.c:243
>  wrap_directory_iterator+0x96/0xe0 fs/readdir.c:65
>  iterate_dir+0x399/0x570 fs/readdir.c:108
>  __do_sys_getdents64 fs/readdir.c:410 [inline]
>  __se_sys_getdents64+0xe4/0x260 fs/readdir.c:396
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f2c837c1833
> Code: c1 66 0f 1f 44 00 00 48 83 c4 08 48 89 ef 5b 5d e9 32 3d f8 ff 66 90 b8 ff ff ff 7f 48 39 c2 48 0f 47 d0 b8 d9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 c7 c2 a8 ff ff ff f7 d8
> RSP: 002b:00007ffc8cf73ff8 EFLAGS: 00000293 ORIG_RAX: 00000000000000d9
> RAX: ffffffffffffffda RBX: 000055557b9dd600 RCX: 00007f2c837c1833
> RDX: 0000000000008000 RSI: 000055557b9dd600 RDI: 0000000000000005
> RBP: 000055557b9dd5d4 R08: 0000000000028a41 R09: 0000000000000000
> R10: 00007f2c839b7cc0 R11: 0000000000000293 R12: ffffffffffffffa8
> R13: 0000000000000010 R14: 000055557b9dd5d0 R15: 00007ffc8cf762b0
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:exfat_convert_ucs2_to_char fs/exfat/nls.c:441 [inline]
> RIP: 0010:__exfat_utf16_to_nls fs/exfat/nls.c:554 [inline]
> RIP: 0010:exfat_utf16_to_nls+0x21c/0x840 fs/exfat/nls.c:638
> Code: 2e 29 ff 66 41 83 fc 7f 77 14 e8 7f 2a 29 ff e9 b6 00 00 00 e8 75 2a 29 ff e9 a9 00 00 00 48 8b 4c 24 40 48 89 c8 48 c1 e8 03 <42> 80 3c 38 00 74 0f 48 8b 7c 24 40 e8 d3 6b 8e ff 48 8b 4c 24 40
> RSP: 0018:ffffc90003fef760 EFLAGS: 00010202
> RAX: 0000000000000002 RBX: 0000000000000004 RCX: 0000000000000010
> RDX: ffff88802f18bc80 RSI: 00000000000000e1 RDI: 0000000000000080
> RBP: ffffc90003fef850 R08: 0000000000000005 R09: 0000000000000000
> R10: ffffc90003fef7e0 R11: fffff520007fdefc R12: 00000000000000e1
> R13: ffffc90003fefa48 R14: 0000000000000000 R15: dffffc0000000000
> FS:  000055557b9c2500(0000) GS:ffff888125a03000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000c000692800 CR3: 00000000734c8000 CR4: 00000000003526f0
> ----------------
> Code disassembly (best guess):
>    0:   2e 29 ff                cs sub %edi,%edi
>    3:   66 41 83 fc 7f          cmp    $0x7f,%r12w
>    8:   77 14                   ja     0x1e
>    a:   e8 7f 2a 29 ff          call   0xff292a8e
>    f:   e9 b6 00 00 00          jmp    0xca
>   14:   e8 75 2a 29 ff          call   0xff292a8e
>   19:   e9 a9 00 00 00          jmp    0xc7
>   1e:   48 8b 4c 24 40          mov    0x40(%rsp),%rcx
>   23:   48 89 c8                mov    %rcx,%rax
>   26:   48 c1 e8 03             shr    $0x3,%rax
> * 2a:   42 80 3c 38 00          cmpb   $0x0,(%rax,%r15,1) <-- trapping instruction
>   2f:   74 0f                   je     0x40
>   31:   48 8b 7c 24 40          mov    0x40(%rsp),%rdi
>   36:   e8 d3 6b 8e ff          call   0xff8e6c0e
>   3b:   48 8b 4c 24 40          mov    0x40(%rsp),%rcx
>
>
> ---
> This report is generated by a bot. It may contain errors.
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>
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>
> If the report is already addressed, let syzbot know by replying with:
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>
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>
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