[moderation/CI] Re: mm, swap: extendable swap devices (xswap phase I)

[syzbot ci <syzbot+ci959f1a5b24994e7e@syzkaller.appspotmail.com>]

syzbot ci has tested the following series

[v5] mm, swap: extendable swap devices (xswap phase I)
https://lore.kernel.org/all/20261109055455.536925-1-baoquan.he@linux.dev
* [PATCH v5 01/19] mm: xswap support for zswap
* [PATCH v5 02/19] mm, swap: refactor free_swap_cluster_info to take swap_info_struct
* [PATCH v5 03/19] mm, swap: add VM_SPARSE cluster-array helpers for xswap
* [PATCH v5 04/19] mm, swap: use a VM_SPARSE cluster array for xswap devices
* [PATCH v5 05/19] mm, swap: widen swap_info_struct max/pages to unsigned long
* [PATCH v5 06/19] mm, swap: add a sysfs interface to create xswap devices
* [PATCH v5 07/19] mm, swap: refactor swapoff and add xswap_destroy
* [PATCH v5 08/19] mm, swap: require zswap for xswap devices
* [PATCH v5 09/19] mm, swap: use a stable id for xswap devices
* [PATCH v5 10/19] mm, swap: let the command line set the xswap device size
* [PATCH v5 11/19] mm, swap: add CONFIG_XSWAP_DEFAULT_MAX
* [PATCH v5 12/19] mm, swap: let swapoff destroy xswap devices by name
* [PATCH v5 13/19] mm, swap: add xswap grow trigger on cluster allocation
* [PATCH v5 14/19] mm, swap: add debugfs counters for xswap
* [PATCH v5 15/19] mm, swap: make xswap cluster_info accesses RCU-safe
* [PATCH v5 16/19] mm, swap: prepare xswap_unmap_clusters for range shrinking
* [PATCH v5 17/19] mm, swap: add xswap shrink trigger and defer it to a workqueue
* [PATCH v5 18/19] mm, swap: do not give an xswap slot to a cgroup that cannot zswap
* [PATCH v5 19/19] mm, swap: skip the overcommit probe when removing xswap

and found the following issue:
BUG: unable to handle kernel paging request in swapoff

Full report is available here:
https://ci.syzbot.org/series/88bad2a7-a1dc-4686-80c1-647e34e90e37

***

BUG: unable to handle kernel paging request in swapoff

tree:      mm-new
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm.git
base:      2dc0136b1fdac153434ab02778fcdb32db5d0dae
arch:      amd64
compiler:  Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
config:    https://ci.syzbot.org/builds/5c923c30-8b6d-49b4-8bbb-014cb85737f7/config
syz repro: https://ci.syzbot.org/findings/f14c26d8-d891-4444-9227-d55cbaf2adb7/syz_repro

BUG: unable to handle page fault for address: fffffffffffffffe
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD ff4b067 P4D ff4b067 PUD ff4d067 PMD 0 
Oops: Oops: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 5894 Comm: syz.2.19 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:__do_sys_swapoff mm/swapfile.c:3743 [inline]
RIP: 0010:__se_sys_swapoff+0x233/0x610 mm/swapfile.c:3719
Code: 99 90 ff e9 42 ff ff ff e8 2a 99 90 ff eb 6f 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 72 c7 08 00 4c 89 64 24 10 <4d> 8b 24 24 66 43 c7 44 2f 04 00 00 43 c6 44 2f 06 00 4c 89 3c 24
RSP: 0018:ffffc90003d1fde0 EFLAGS: 00010246
RAX: 1fffffffffffffff RBX: 0000200000000000 RCX: c8af1e162af39c00
RDX: 0000000000000000 RSI: fffffffffffffffe RDI: 00000000ffffff9c
RBP: ffffc90003d1fee0 R08: 0000000000000003 R09: 0000000000000000
R10: ffffc90003d1fd40 R11: fffff520007a3faa R12: fffffffffffffffe
R13: dffffc0000000000 R14: fffffffffffffffe R15: 1ffff920007a3fc0
FS:  00007f5ca62c96c0(0000) GS:ffff8882a7806000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffffe CR3: 00000001023f4000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5ca53a8f19
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:00007f5ca62c9028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a8
RAX: ffffffffffffffda RBX: 00007f5ca5625fa0 RCX: 00007f5ca53a8f19
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000000
RBP: 00007f5ca5437f6d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5ca5626038 R14: 00007f5ca5625fa0 R15: 00007ffce4301208
 </TASK>
Modules linked in:
CR2: fffffffffffffffe
---[ end trace 0000000000000000 ]---
RIP: 0010:__do_sys_swapoff mm/swapfile.c:3743 [inline]
RIP: 0010:__se_sys_swapoff+0x233/0x610 mm/swapfile.c:3719
Code: 99 90 ff e9 42 ff ff ff e8 2a 99 90 ff eb 6f 4c 89 e0 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 e7 e8 72 c7 08 00 4c 89 64 24 10 <4d> 8b 24 24 66 43 c7 44 2f 04 00 00 43 c6 44 2f 06 00 4c 89 3c 24
RSP: 0018:ffffc90003d1fde0 EFLAGS: 00010246
RAX: 1fffffffffffffff RBX: 0000200000000000 RCX: c8af1e162af39c00
RDX: 0000000000000000 RSI: fffffffffffffffe RDI: 00000000ffffff9c
RBP: ffffc90003d1fee0 R08: 0000000000000003 R09: 0000000000000000
R10: ffffc90003d1fd40 R11: fffff520007a3faa R12: fffffffffffffffe
R13: dffffc0000000000 R14: fffffffffffffffe R15: 1ffff920007a3fc0
FS:  00007f5ca62c96c0(0000) GS:ffff8882a7806000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffffffffffe CR3: 00000001023f4000 CR4: 00000000000006f0
----------------
Code disassembly (best guess), 3 bytes skipped:
   0:	e9 42 ff ff ff       	jmp    0xffffff47
   5:	e8 2a 99 90 ff       	call   0xff909934
   a:	eb 6f                	jmp    0x7b
   c:	4c 89 e0             	mov    %r12,%rax
   f:	48 c1 e8 03          	shr    $0x3,%rax
  13:	42 80 3c 28 00       	cmpb   $0x0,(%rax,%r13,1)
  18:	74 08                	je     0x22
  1a:	4c 89 e7             	mov    %r12,%rdi
  1d:	e8 72 c7 08 00       	call   0x8c794
  22:	4c 89 64 24 10       	mov    %r12,0x10(%rsp)
* 27:	4d 8b 24 24          	mov    (%r12),%r12 <-- trapping instruction
  2b:	66 43 c7 44 2f 04 00 	movw   $0x0,0x4(%r15,%r13,1)
  32:	00
  33:	43 c6 44 2f 06 00    	movb   $0x0,0x6(%r15,%r13,1)
  39:	4c 89 3c 24          	mov    %r15,(%rsp)


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: syzbot@syzkaller.appspotmail.com

---
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