[moderation] [fs?] BUG: unable to handle kernel paging request in poll_freewait

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ccd1cdca5cd4 Merge tag 'nfsd-6.19-1' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=127ec8fc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a11e0f726bfb6765
dashboard link: https://syzkaller.appspot.com/bug?extid=ad9267e787bde6cef227
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a30893dc5d92/disk-ccd1cdca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/64a722042ed2/vmlinux-ccd1cdca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bf3d1ced5d9f/bzImage-ccd1cdca.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ad9267...@syzkaller.appspotmail.com

BUG: unable to handle page fault for address: ffff887ffffffff8
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: Oops: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5797 Comm: syz-executor Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:free_poll_entry fs/select.c:132 [inline]
RIP: 0010:poll_freewait+0x172/0x250 fs/select.c:149
Code: 00 00 00 48 8b 6b 08 4c 8d 6b 10 e8 98 c4 7c ff 48 83 ed 40 48 8d 7d 38 48 8d 75 10 48 89 f8 48 c1 e8 03 42 80 3c 20 00 75 65 <48> 8b 7d 38 e8 05 ec 53 ff 48 89 e8 48 c1 e8 03 42 80 3c 20 00 75
RSP: 0018:ffffc900034a7630 EFLAGS: 00010246
RAX: 1ffff10fffffffff RBX: ffff8880561bc000 RCX: ffffffff82422193
RDX: ffff8880672ba4c0 RSI: ffff887fffffffd0 RDI: ffff887ffffffff8
RBP: ffff887fffffffc0 R08: 0000000000000004 R09: 0000000000000009
R10: 0000000000000009 R11: ffff8880672baff0 R12: dffffc0000000000
R13: ffff8880561bc010 R14: 0000000000000009 R15: ffffc900034a7810
FS: 0000555563d7f500(0000) GS:ffff8881248f5000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff887ffffffff8 CR3: 0000000033490000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: fffffffffffffffc DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
do_select+0xe52/0x17e0 fs/select.c:608
core_sys_select+0x453/0xc20 fs/select.c:677
do_pselect.constprop.0+0x19f/0x1e0 fs/select.c:759
__do_sys_pselect6 fs/select.c:798 [inline]
__se_sys_pselect6 fs/select.c:789 [inline]
__x64_sys_pselect6+0x182/0x240 fs/select.c:789
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc2eb98f50c
Code: 29 44 24 30 80 3d 6b c0 22 00 00 4c 89 4c 24 40 4c 8d 4c 24 40 48 c7 44 24 48 08 00 00 00 74 2e 4c 89 ea b8 0e 01 00 00 0f 05 <48> 3d 00 f0 ff ff 77 7c 48 8b 54 24 58 64 48 2b 14 25 28 00 00 00
RSP: 002b:00007ffeeca28780 EFLAGS: 00000202 ORIG_RAX: 000000000000010e
RAX: ffffffffffffffda RBX: 00007ffeeca28d00 RCX: 00007fc2eb98f50c
RDX: 0000000000000000 RSI: 00007ffeeca288b0 RDI: 0000000000000026
RBP: 00007ffeeca288b0 R08: 00007ffeeca287b0 R09: 00007ffeeca287c0
R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffeeca28b50
R13: 0000000000000000 R14: 00007ffeeca28bd0 R15: 585858582e7a7973
</TASK>
Modules linked in:
CR2: ffff887ffffffff8
---[ end trace 0000000000000000 ]---
RIP: 0010:free_poll_entry fs/select.c:132 [inline]
RIP: 0010:poll_freewait+0x172/0x250 fs/select.c:149
Code: 00 00 00 48 8b 6b 08 4c 8d 6b 10 e8 98 c4 7c ff 48 83 ed 40 48 8d 7d 38 48 8d 75 10 48 89 f8 48 c1 e8 03 42 80 3c 20 00 75 65 <48> 8b 7d 38 e8 05 ec 53 ff 48 89 e8 48 c1 e8 03 42 80 3c 20 00 75
RSP: 0018:ffffc900034a7630 EFLAGS: 00010246
RAX: 1ffff10fffffffff RBX: ffff8880561bc000 RCX: ffffffff82422193
RDX: ffff8880672ba4c0 RSI: ffff887fffffffd0 RDI: ffff887ffffffff8
RBP: ffff887fffffffc0 R08: 0000000000000004 R09: 0000000000000009
R10: 0000000000000009 R11: ffff8880672baff0 R12: dffffc0000000000
R13: ffff8880561bc010 R14: 0000000000000009 R15: ffffc900034a7810
FS: 0000555563d7f500(0000) GS:ffff8881248f5000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff887ffffffff8 CR3: 0000000033490000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: fffffffffffffffc DR6: 00000000ffff0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 00 00 add %al,(%rax)
2: 00 48 8b add %cl,-0x75(%rax)
5: 6b 08 4c imul $0x4c,(%rax),%ecx
8: 8d 6b 10 lea 0x10(%rbx),%ebp
b: e8 98 c4 7c ff call 0xff7cc4a8
10: 48 83 ed 40 sub $0x40,%rbp
14: 48 8d 7d 38 lea 0x38(%rbp),%rdi
18: 48 8d 75 10 lea 0x10(%rbp),%rsi
1c: 48 89 f8 mov %rdi,%rax
1f: 48 c1 e8 03 shr $0x3,%rax
23: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)
28: 75 65 jne 0x8f
* 2a: 48 8b 7d 38 mov 0x38(%rbp),%rdi <-- trapping instruction
2e: e8 05 ec 53 ff call 0xff53ec38
33: 48 89 e8 mov %rbp,%rax
36: 48 c1 e8 03 shr $0x3,%rax
3a: 42 80 3c 20 00 cmpb $0x0,(%rax,%r12,1)
3f: 75 .byte 0x75


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