[moderation/CI] Re: Virtual Swap Space (Swap Table Edition)

[moderation/CI] Re: Virtual Swap Space (Swap Table Edition)

[syzbot ci]

syzbot ci has tested the following series

[v3] Virtual Swap Space (Swap Table Edition)
https://lore.kernel.org/all/20260806184254.3790858-1-nphamcs@gmail.com
* [PATCH v3 01/11] mm, swap: add virtual swap device infrastructure
* [PATCH v3 02/11] mm, swap: support zswap and zeroswap as vswap backends
* [PATCH v3 03/11] mm, swap: prepare the swap IO path for vswap
* [PATCH v3 04/11] mm, swap: support physical swap as a vswap backend
* [PATCH v3 05/11] mm, swap: enable THP swapin for vswap entries
* [PATCH v3 06/11] mm, swap: write back vswap zswap entries to physical swap
* [PATCH v3 07/11] mm, swap: reclaim physical slots backing cache-only vswap entries
* [PATCH v3 08/11] mm, swap: only charge physical swap entries
* [PATCH v3 09/11] mm, swap: add debugfs counters for vswap
* [PATCH v3 10/11] mm, swap: defer memcg_table allocation for physical swap clusters
* [PATCH v3 11/11] mm, swap: widen swap_info_struct max/pages to unsigned long

and found the following issue:
KASAN: null-ptr-deref Read in swap_entry_backend_has_flag

Full report is available here:
https://ci.syzbot.org/series/e7da1097-3230-4e50-80cb-1dfafeebea40

***

KASAN: null-ptr-deref Read in swap_entry_backend_has_flag

tree:      linux-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next
base:      bacc32cc7de65ffff70080a48eb294f89e434d5e
arch:      amd64
compiler:  Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
config:    https://ci.syzbot.org/builds/4f943657-9481-4637-9b1f-9be1bff18f92/config
syz repro: https://ci.syzbot.org/findings/f6c4f1ab-951c-4759-b397-e22c23c3bf32/syz_repro

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:82 [inline]
BUG: KASAN: null-ptr-deref in atomic_long_read include/linux/atomic/atomic-instrumented.h:3188 [inline]
BUG: KASAN: null-ptr-deref in __vtable_get mm/vswap.h:147 [inline]
BUG: KASAN: null-ptr-deref in vswap_to_phys mm/vswap.h:197 [inline]
BUG: KASAN: null-ptr-deref in swap_entry_backend_has_flag+0xfe/0x220 mm/vswap.h:441
Read of size 8 at addr 0000000000000000 by task syz.2.20/5818

CPU: 1 UID: 0 PID: 5818 Comm: syz.2.20 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
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
 instrument_atomic_read include/linux/instrumented.h:82 [inline]
 atomic_long_read include/linux/atomic/atomic-instrumented.h:3188 [inline]
 __vtable_get mm/vswap.h:147 [inline]
 vswap_to_phys mm/vswap.h:197 [inline]
 swap_entry_backend_has_flag+0xfe/0x220 mm/vswap.h:441
 do_swap_page+0x3c0/0x5620 mm/memory.c:4975
 __collapse_huge_page_swapin mm/khugepaged.c:1202 [inline]
 collapse_huge_page mm/khugepaged.c:1325 [inline]
 mthp_collapse mm/khugepaged.c:1524 [inline]
 collapse_scan_pmd mm/khugepaged.c:1786 [inline]
 collapse_single_pmd+0x24c6/0x3da0 mm/khugepaged.c:2803
 madvise_collapse+0x2cf/0x790 mm/khugepaged.c:3237
 madvise_vma_behavior+0x115f/0x4170 mm/madvise.c:1363
 madvise_walk_vmas+0x576/0xb00 mm/madvise.c:1712
 madvise_do_behavior+0x385/0x540 mm/madvise.c:1907
 do_madvise+0x327/0x3a0 mm/madvise.c:2005
 __do_sys_madvise mm/madvise.c:2014 [inline]
 __se_sys_madvise mm/madvise.c:2012 [inline]
 __x64_sys_madvise+0xa6/0xc0 mm/madvise.c:2012
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbcad79e019
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:00007fbcae5c4028 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007fbcada25fa0 RCX: 00007fbcad79e019
RDX: 0000000000000019 RSI: 0000000000c00000 RDI: 0000200000000000
RBP: 00007fbcad83500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbcada26038 R14: 00007fbcada25fa0 R15: 00007fff095fa0b8
 </TASK>
==================================================================


***

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

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.

To test a patch for this bug, please reply with `#syz test`
(should be on a separate line).

The patch should be attached to the email.
Note: arguments like custom git repos and branches are not supported.

The email will later be sent to:
[akpm@linux-foundation.org axelrasmussen@google.com baohua@kernel.org baoquan.he@linux.dev cgroups@vger.kernel.org chengming.zhou@linux.dev chrisl@kernel.org corbet@lwn.net david@kernel.org gourry@gourry.net hannes@cmpxchg.org haowenchao22@gmail.com kasong@tencent.com kernel-team@meta.com liam@infradead.org linux-doc@vger.kernel.org linux-kernel@vger.kernel.org linux-mm@kvack.org ljs@kernel.org mhocko@kernel.org muchun.song@linux.dev nphamcs@gmail.com qi.zheng@linux.dev riel@surriel.com roman.gushchin@linux.dev rppt@kernel.org shakeel.butt@linux.dev shikemeng@huaweicloud.com surenb@google.com vbabka@kernel.org weixugc@google.com yosry@kernel.org youngjun.park@lge.com yuanchu@google.com]

If the report looks fine to you, reply with:
#syz upstream

If the report is a false positive, reply with
#syz invalid

Re: [moderation/CI] Re: Virtual Swap Space (Swap Table Edition)

[Pimyn Girgis]

#syz upstream


On Fri, Aug 7, 2026 at 4:12 AM syzbot ci
<syzbot+ci0044aa36144eea42@syzkaller.appspotmail.com> wrote:
>
> syzbot ci has tested the following series
>
> [v3] Virtual Swap Space (Swap Table Edition)
> https://lore.kernel.org/all/20260806184254.3790858-1-nphamcs@gmail.com
> * [PATCH v3 01/11] mm, swap: add virtual swap device infrastructure
> * [PATCH v3 02/11] mm, swap: support zswap and zeroswap as vswap backends
> * [PATCH v3 03/11] mm, swap: prepare the swap IO path for vswap
> * [PATCH v3 04/11] mm, swap: support physical swap as a vswap backend
> * [PATCH v3 05/11] mm, swap: enable THP swapin for vswap entries
> * [PATCH v3 06/11] mm, swap: write back vswap zswap entries to physical swap
> * [PATCH v3 07/11] mm, swap: reclaim physical slots backing cache-only vswap entries
> * [PATCH v3 08/11] mm, swap: only charge physical swap entries
> * [PATCH v3 09/11] mm, swap: add debugfs counters for vswap
> * [PATCH v3 10/11] mm, swap: defer memcg_table allocation for physical swap clusters
> * [PATCH v3 11/11] mm, swap: widen swap_info_struct max/pages to unsigned long
>
> and found the following issue:
> KASAN: null-ptr-deref Read in swap_entry_backend_has_flag
>
> Full report is available here:
> https://ci.syzbot.org/series/e7da1097-3230-4e50-80cb-1dfafeebea40
>
> ***
>
> KASAN: null-ptr-deref Read in swap_entry_backend_has_flag
>
> tree:      linux-next
> URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next
> base:      bacc32cc7de65ffff70080a48eb294f89e434d5e
> arch:      amd64
> compiler:  Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
> config:    https://ci.syzbot.org/builds/4f943657-9481-4637-9b1f-9be1bff18f92/config
> syz repro: https://ci.syzbot.org/findings/f6c4f1ab-951c-4759-b397-e22c23c3bf32/syz_repro
>
> ==================================================================
> BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:82 [inline]
> BUG: KASAN: null-ptr-deref in atomic_long_read include/linux/atomic/atomic-instrumented.h:3188 [inline]
> BUG: KASAN: null-ptr-deref in __vtable_get mm/vswap.h:147 [inline]
> BUG: KASAN: null-ptr-deref in vswap_to_phys mm/vswap.h:197 [inline]
> BUG: KASAN: null-ptr-deref in swap_entry_backend_has_flag+0xfe/0x220 mm/vswap.h:441
> Read of size 8 at addr 0000000000000000 by task syz.2.20/5818
>
> CPU: 1 UID: 0 PID: 5818 Comm: syz.2.20 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
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
>  kasan_report+0x117/0x150 mm/kasan/report.c:595
>  check_region_inline mm/kasan/generic.c:-1 [inline]
>  kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
>  instrument_atomic_read include/linux/instrumented.h:82 [inline]
>  atomic_long_read include/linux/atomic/atomic-instrumented.h:3188 [inline]
>  __vtable_get mm/vswap.h:147 [inline]
>  vswap_to_phys mm/vswap.h:197 [inline]
>  swap_entry_backend_has_flag+0xfe/0x220 mm/vswap.h:441
>  do_swap_page+0x3c0/0x5620 mm/memory.c:4975
>  __collapse_huge_page_swapin mm/khugepaged.c:1202 [inline]
>  collapse_huge_page mm/khugepaged.c:1325 [inline]
>  mthp_collapse mm/khugepaged.c:1524 [inline]
>  collapse_scan_pmd mm/khugepaged.c:1786 [inline]
>  collapse_single_pmd+0x24c6/0x3da0 mm/khugepaged.c:2803
>  madvise_collapse+0x2cf/0x790 mm/khugepaged.c:3237
>  madvise_vma_behavior+0x115f/0x4170 mm/madvise.c:1363
>  madvise_walk_vmas+0x576/0xb00 mm/madvise.c:1712
>  madvise_do_behavior+0x385/0x540 mm/madvise.c:1907
>  do_madvise+0x327/0x3a0 mm/madvise.c:2005
>  __do_sys_madvise mm/madvise.c:2014 [inline]
>  __se_sys_madvise mm/madvise.c:2012 [inline]
>  __x64_sys_madvise+0xa6/0xc0 mm/madvise.c:2012
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fbcad79e019
> 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:00007fbcae5c4028 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
> RAX: ffffffffffffffda RBX: 00007fbcada25fa0 RCX: 00007fbcad79e019
> RDX: 0000000000000019 RSI: 0000000000c00000 RDI: 0000200000000000
> RBP: 00007fbcad83500c R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fbcada26038 R14: 00007fbcada25fa0 R15: 00007fff095fa0b8
>  </TASK>
> ==================================================================
>
>
> ***
>
> 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
>
> ---
> This report is generated by a bot. It may contain errors.
> syzbot ci engineers can be reached at syzkaller@googlegroups.com.
>
> To test a patch for this bug, please reply with `#syz test`
> (should be on a separate line).
>
> The patch should be attached to the email.
> Note: arguments like custom git repos and branches are not supported.
>
> The email will later be sent to:
> [akpm@linux-foundation.org axelrasmussen@google.com baohua@kernel.org baoquan.he@linux.dev cgroups@vger.kernel.org chengming.zhou@linux.dev chrisl@kernel.org corbet@lwn.net david@kernel.org gourry@gourry.net hannes@cmpxchg.org haowenchao22@gmail.com kasong@tencent.com kernel-team@meta.com liam@infradead.org linux-doc@vger.kernel.org linux-kernel@vger.kernel.org linux-mm@kvack.org ljs@kernel.org mhocko@kernel.org muchun.song@linux.dev nphamcs@gmail.com qi.zheng@linux.dev riel@surriel.com roman.gushchin@linux.dev rppt@kernel.org shakeel.butt@linux.dev shikemeng@huaweicloud.com surenb@google.com vbabka@kernel.org weixugc@google.com yosry@kernel.org youngjun.park@lge.com yuanchu@google.com]
>
> If the report looks fine to you, reply with:
> #syz upstream
>
> If the report is a false positive, reply with
> #syz invalid
>
> --
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-- 
Ⲡⲟⲓⲙⲏⲛ Ⲅⲉⲱⲣⲅⲓⲟⲥ - Pimyn Girgis
Software Engineer
Kernel Dynamic Analysis
pimyn@google.com