[syzbot] [mm?] kernel BUG in collapse_scan_file

[syzbot <syzbot+8961cb270ae74b4129fb@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    95c541ddfb08 Add linux-next specific files for 20260316
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15ccc216580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ed431987028345c6
dashboard link: https://syzkaller.appspot.com/bug?extid=8961cb270ae74b4129fb
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=12f778da580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12cc006a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c40f27ad73d8/disk-95c541dd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bd811888f684/vmlinux-95c541dd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3b72363d7dbd/bzImage-95c541dd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8961cb270ae74b4129fb@syzkaller.appspotmail.com

node ffff88805d558b00 offset 0 parent ffff88805d558840 shift 0 count 3 values 0 array ffff88807a8195c0 list ffff88805d558b18 ffff88805d558b18 marks 0 0 0
------------[ cut here ]------------
kernel BUG at ./include/linux/xarray.h:1441!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 6001 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:XAS_INVALID include/linux/xarray.h:1441 [inline]
RIP: 0010:collapse_file mm/khugepaged.c:2055 [inline]
RIP: 0010:collapse_scan_file+0x4f98/0x5230 mm/khugepaged.c:2404
Code: ff 4c 89 e7 48 c7 c6 60 b2 dc 8b e8 82 62 f1 fe 90 0f 0b 48 85 db 0f 84 03 01 00 00 e8 71 e5 8f ff 48 89 df e8 a9 20 7b 09 90 <0f> 0b e8 61 e5 8f ff 48 89 df 48 c7 c6 60 b2 dc 8b e8 52 62 f1 fe
RSP: 0018:ffffc90003826e20 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88805d558b00 RCX: a13f20bd39c5a100
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc90003827130 R08: ffffc90003826ba7 R09: 1ffff92000704d74
R10: dffffc0000000000 R11: fffff52000704d75 R12: ffffea0001b678f0
R13: dffffc0000000000 R14: 0000000000000000 R15: ffffc90003827010
FS:  000055557e3c2500(0000) GS:ffff888125437000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000b000 CR3: 000000007ac66000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 collapse_single_pmd+0x22b/0x4510 mm/khugepaged.c:2437
 madvise_collapse+0x34c/0x820 mm/khugepaged.c:2859
 madvise_vma_behavior+0x1094/0x4460 mm/madvise.c:1362
 madvise_walk_vmas+0x573/0xae0 mm/madvise.c:1711
 madvise_do_behavior+0x386/0x540 mm/madvise.c:1927
 do_madvise+0x1fa/0x2e0 mm/madvise.c:2020
 __do_sys_madvise mm/madvise.c:2029 [inline]
 __se_sys_madvise mm/madvise.c:2027 [inline]
 __x64_sys_madvise+0xa6/0xc0 mm/madvise.c:2027
 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: 0033:0x7f90d419c799
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:00007ffd50711398 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007f90d4415fa0 RCX: 00007f90d419c799
RDX: 0000000000000019 RSI: 0000000000600003 RDI: 0000200000000000
RBP: 00007f90d4232c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f90d4415fac R14: 00007f90d4415fa0 R15: 00007f90d4415fa0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:XAS_INVALID include/linux/xarray.h:1441 [inline]
RIP: 0010:collapse_file mm/khugepaged.c:2055 [inline]
RIP: 0010:collapse_scan_file+0x4f98/0x5230 mm/khugepaged.c:2404
Code: ff 4c 89 e7 48 c7 c6 60 b2 dc 8b e8 82 62 f1 fe 90 0f 0b 48 85 db 0f 84 03 01 00 00 e8 71 e5 8f ff 48 89 df e8 a9 20 7b 09 90 <0f> 0b e8 61 e5 8f ff 48 89 df 48 c7 c6 60 b2 dc 8b e8 52 62 f1 fe
RSP: 0018:ffffc90003826e20 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88805d558b00 RCX: a13f20bd39c5a100
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: ffffc90003827130 R08: ffffc90003826ba7 R09: 1ffff92000704d74
R10: dffffc0000000000 R11: fffff52000704d75 R12: ffffea0001b678f0
R13: dffffc0000000000 R14: 0000000000000000 R15: ffffc90003827010
FS:  000055557e3c2500(0000) GS:ffff888125537000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8156602000 CR3: 000000007ac66000 CR4: 00000000003526f0


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