* [moderation/CI] Re: memcg: fix dying memcg pinned by swapped out shmem pages
@ 2026-08-13 13:24 syzbot ci
2026-08-13 13:25 ` Pimyn Girgis
0 siblings, 1 reply; 2+ messages in thread
From: syzbot ci @ 2026-08-13 13:24 UTC (permalink / raw)
To: syzkaller-upstream-moderation; +Cc: syzbot
syzbot ci has tested the following series
[v1] memcg: fix dying memcg pinned by swapped out shmem pages
https://lore.kernel.org/all/20260813-memcgid-objcg-v1-0-83d21c685b77@tencent.com
* [PATCH RFC 1/5] memcg: move memcg private ID refcount to objcg
* [PATCH RFC 2/5] memcg: get stable memcg first before getting memcgid reference
* [PATCH RFC 3/5] memcg: remove retry logic in mem_cgroup_private_id_get_online
* [PATCH RFC 4/5] memcg: add a helper to get online memcg from memcgid
* [PATCH RFC 5/5] memcg: filter out reparented memcgs got using memcgid
and found the following issue:
WARNING: refcount bug in __mem_cgroup_uncharge_swap
Full report is available here:
https://ci.syzbot.org/series/3a8a2a5f-8b6d-4abf-954e-a1a18ee62748
***
WARNING: refcount bug in __mem_cgroup_uncharge_swap
tree: linux-next
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next
base: 288058d8db5d35623228d84f48d9bea3707d5c85
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/35dac6f6-b44a-4ea8-9adf-2cdda5584e45/config
syz repro: https://ci.syzbot.org/findings/6e117c0b-d6e2-44a6-8e35-161cb33f2aff/syz_repro
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28, CPU#0: syz.2.19/5863
Modules linked in:
CPU: 0 UID: 0 PID: 5863 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:refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28
Code: 64 84 8e 0b 67 48 0f b9 3a eb 4a e8 58 fa f2 fc 48 8d 3d 61 84 8e 0b 67 48 0f b9 3a eb 37 e8 45 fa f2 fc 48 8d 3d 5e 84 8e 0b <67> 48 0f b9 3a eb 24 e8 32 fa f2 fc 48 8d 3d 5b 84 8e 0b 67 48 0f
RSP: 0018:ffffc90003bbf1d0 EFLAGS: 00010293
RAX: ffffffff84d3ed9b RBX: 0000000000000003 RCX: ffff8881bdf58000
RDX: 0000000000000000 RSI: ffffffff8f363380 RDI: ffffffff90627200
RBP: 1ffffffff20ae968 R08: ffff8881bdf58000 R09: 0000000000000005
R10: 0000000000000004 R11: 0000000000000000 R12: ffff8881026f8000
R13: ffff88810a914100 R14: ffff88810a914134 R15: 1ffff110204df009
FS: 00007fe2ee63d6c0(0000) GS:ffff88818d960000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056066247f0b8 CR3: 000000000e946000 CR4: 00000000000006f0
Call Trace:
<TASK>
mem_cgroup_take_from_private_id mm/memcontrol.c:4049 [inline]
__mem_cgroup_uncharge_swap+0x204/0x2a0 mm/memcontrol.c:5707
mem_cgroup_uncharge_swap include/linux/swap.h:520 [inline]
__swap_cluster_free_entries+0x735/0xc50 mm/swapfile.c:1955
swap_put_entries_cluster+0x3b1/0x4b0 mm/swapfile.c:1629
swap_put_entries_direct+0x137/0x210 mm/swapfile.c:2139
zap_nonpresent_ptes mm/memory.c:1838 [inline]
do_zap_pte_range mm/memory.c:1905 [inline]
zap_pte_range mm/memory.c:2003 [inline]
zap_pmd_range mm/memory.c:2089 [inline]
zap_pud_range mm/memory.c:2117 [inline]
zap_p4d_range mm/memory.c:2138 [inline]
__zap_vma_range+0x1d9d/0x4f10 mm/memory.c:2178
unmap_vmas+0x390/0x550 mm/memory.c:2247
exit_mmap+0x293/0x9f0 mm/mmap.c:1315
__mmput+0x118/0x420 kernel/fork.c:1187
exit_mm+0x221/0x2d0 kernel/exit.c:615
do_exit+0x6cd/0x2360 kernel/exit.c:997
do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
get_signal+0x121b/0x12c0 kernel/signal.c:3046
arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
exit_to_user_mode_loop+0x104/0x730 kernel/entry/common.c:101
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe2ed79e0d9
Code: Unable to access opcode bytes at 0x7fe2ed79e0af.
RSP: 002b:00007fe2ee63d0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007fe2eda25fa8 RCX: 00007fe2ed79e0d9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fe2eda25fa8
RBP: 00007fe2eda25fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe2eda26038 R14: 00007fff0bed41b0 R15: 00007fff0bed4298
</TASK>
----------------
Code disassembly (best guess):
0: 64 84 8e 0b 67 48 0f test %cl,%fs:0xf48670b(%rsi)
7: b9 3a eb 4a e8 mov $0xe84aeb3a,%ecx
c: 58 pop %rax
d: fa cli
e: f2 fc repnz cld
10: 48 8d 3d 61 84 8e 0b lea 0xb8e8461(%rip),%rdi # 0xb8e8478
17: 67 48 0f b9 3a ud1 (%edx),%rdi
1c: eb 37 jmp 0x55
1e: e8 45 fa f2 fc call 0xfcf2fa68
23: 48 8d 3d 5e 84 8e 0b lea 0xb8e845e(%rip),%rdi # 0xb8e8488
* 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2f: eb 24 jmp 0x55
31: e8 32 fa f2 fc call 0xfcf2fa68
36: 48 8d 3d 5b 84 8e 0b lea 0xb8e845b(%rip),%rdi # 0xb8e8498
3d: 67 addr32
3e: 48 rex.W
3f: 0f .byte 0xf
***
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 fix for this bug, please reply with `#syz test`
(on a separate line) and attach the patch to the email.
Notes:
- The patch will be applied on top of the tested series (as an
incremental fix).
- To test a new version of the whole series, please send it directly
to syzbot@lists.linux.dev.
- 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 bfguo@icloud.com bingfangguo@tencent.com cgroups@vger.kernel.org david@fromorbit.com david@kernel.org devnull@kernel.org hannes@cmpxchg.org kasong@tencent.com linux-kernel@vger.kernel.org linux-mm@kvack.org ljs@kernel.org mhocko@kernel.org muchun.song@linux.dev qi.zheng@linux.dev roman.gushchin@linux.dev shakeel.butt@linux.dev weixugc@google.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
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [moderation/CI] Re: memcg: fix dying memcg pinned by swapped out shmem pages
2026-08-13 13:24 [moderation/CI] Re: memcg: fix dying memcg pinned by swapped out shmem pages syzbot ci
@ 2026-08-13 13:25 ` Pimyn Girgis
0 siblings, 0 replies; 2+ messages in thread
From: Pimyn Girgis @ 2026-08-13 13:25 UTC (permalink / raw)
To: syzbot ci; +Cc: syzkaller-upstream-moderation, syzbot
#syz upstream
On Thu, Aug 13, 2026 at 3:24 PM syzbot ci
<syzbot+ci495064e28a773da2@syzkaller.appspotmail.com> wrote:
>
> syzbot ci has tested the following series
>
> [v1] memcg: fix dying memcg pinned by swapped out shmem pages
> https://lore.kernel.org/all/20260813-memcgid-objcg-v1-0-83d21c685b77@tencent.com
> * [PATCH RFC 1/5] memcg: move memcg private ID refcount to objcg
> * [PATCH RFC 2/5] memcg: get stable memcg first before getting memcgid reference
> * [PATCH RFC 3/5] memcg: remove retry logic in mem_cgroup_private_id_get_online
> * [PATCH RFC 4/5] memcg: add a helper to get online memcg from memcgid
> * [PATCH RFC 5/5] memcg: filter out reparented memcgs got using memcgid
>
> and found the following issue:
> WARNING: refcount bug in __mem_cgroup_uncharge_swap
>
> Full report is available here:
> https://ci.syzbot.org/series/3a8a2a5f-8b6d-4abf-954e-a1a18ee62748
>
> ***
>
> WARNING: refcount bug in __mem_cgroup_uncharge_swap
>
> tree: linux-next
> URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next
> base: 288058d8db5d35623228d84f48d9bea3707d5c85
> 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/35dac6f6-b44a-4ea8-9adf-2cdda5584e45/config
> syz repro: https://ci.syzbot.org/findings/6e117c0b-d6e2-44a6-8e35-161cb33f2aff/syz_repro
>
> ------------[ cut here ]------------
> refcount_t: underflow; use-after-free.
> WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28, CPU#0: syz.2.19/5863
> Modules linked in:
> CPU: 0 UID: 0 PID: 5863 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:refcount_warn_saturate+0xb2/0x110 lib/refcount.c:28
> Code: 64 84 8e 0b 67 48 0f b9 3a eb 4a e8 58 fa f2 fc 48 8d 3d 61 84 8e 0b 67 48 0f b9 3a eb 37 e8 45 fa f2 fc 48 8d 3d 5e 84 8e 0b <67> 48 0f b9 3a eb 24 e8 32 fa f2 fc 48 8d 3d 5b 84 8e 0b 67 48 0f
> RSP: 0018:ffffc90003bbf1d0 EFLAGS: 00010293
> RAX: ffffffff84d3ed9b RBX: 0000000000000003 RCX: ffff8881bdf58000
> RDX: 0000000000000000 RSI: ffffffff8f363380 RDI: ffffffff90627200
> RBP: 1ffffffff20ae968 R08: ffff8881bdf58000 R09: 0000000000000005
> R10: 0000000000000004 R11: 0000000000000000 R12: ffff8881026f8000
> R13: ffff88810a914100 R14: ffff88810a914134 R15: 1ffff110204df009
> FS: 00007fe2ee63d6c0(0000) GS:ffff88818d960000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000056066247f0b8 CR3: 000000000e946000 CR4: 00000000000006f0
> Call Trace:
> <TASK>
> mem_cgroup_take_from_private_id mm/memcontrol.c:4049 [inline]
> __mem_cgroup_uncharge_swap+0x204/0x2a0 mm/memcontrol.c:5707
> mem_cgroup_uncharge_swap include/linux/swap.h:520 [inline]
> __swap_cluster_free_entries+0x735/0xc50 mm/swapfile.c:1955
> swap_put_entries_cluster+0x3b1/0x4b0 mm/swapfile.c:1629
> swap_put_entries_direct+0x137/0x210 mm/swapfile.c:2139
> zap_nonpresent_ptes mm/memory.c:1838 [inline]
> do_zap_pte_range mm/memory.c:1905 [inline]
> zap_pte_range mm/memory.c:2003 [inline]
> zap_pmd_range mm/memory.c:2089 [inline]
> zap_pud_range mm/memory.c:2117 [inline]
> zap_p4d_range mm/memory.c:2138 [inline]
> __zap_vma_range+0x1d9d/0x4f10 mm/memory.c:2178
> unmap_vmas+0x390/0x550 mm/memory.c:2247
> exit_mmap+0x293/0x9f0 mm/mmap.c:1315
> __mmput+0x118/0x420 kernel/fork.c:1187
> exit_mm+0x221/0x2d0 kernel/exit.c:615
> do_exit+0x6cd/0x2360 kernel/exit.c:997
> do_group_exit+0x22d/0x2f0 kernel/exit.c:1152
> get_signal+0x121b/0x12c0 kernel/signal.c:3046
> arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
> __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
> exit_to_user_mode_loop+0x104/0x730 kernel/entry/common.c:101
> __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
> syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
> syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
> do_syscall_64+0x353/0x580 arch/x86/entry/syscall_64.c:100
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fe2ed79e0d9
> Code: Unable to access opcode bytes at 0x7fe2ed79e0af.
> RSP: 002b:00007fe2ee63d0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: fffffffffffffe00 RBX: 00007fe2eda25fa8 RCX: 00007fe2ed79e0d9
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fe2eda25fa8
> RBP: 00007fe2eda25fa0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fe2eda26038 R14: 00007fff0bed41b0 R15: 00007fff0bed4298
> </TASK>
> ----------------
> Code disassembly (best guess):
> 0: 64 84 8e 0b 67 48 0f test %cl,%fs:0xf48670b(%rsi)
> 7: b9 3a eb 4a e8 mov $0xe84aeb3a,%ecx
> c: 58 pop %rax
> d: fa cli
> e: f2 fc repnz cld
> 10: 48 8d 3d 61 84 8e 0b lea 0xb8e8461(%rip),%rdi # 0xb8e8478
> 17: 67 48 0f b9 3a ud1 (%edx),%rdi
> 1c: eb 37 jmp 0x55
> 1e: e8 45 fa f2 fc call 0xfcf2fa68
> 23: 48 8d 3d 5e 84 8e 0b lea 0xb8e845e(%rip),%rdi # 0xb8e8488
> * 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
> 2f: eb 24 jmp 0x55
> 31: e8 32 fa f2 fc call 0xfcf2fa68
> 36: 48 8d 3d 5b 84 8e 0b lea 0xb8e845b(%rip),%rdi # 0xb8e8498
> 3d: 67 addr32
> 3e: 48 rex.W
> 3f: 0f .byte 0xf
>
>
> ***
>
> 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 fix for this bug, please reply with `#syz test`
> (on a separate line) and attach the patch to the email.
>
> Notes:
> - The patch will be applied on top of the tested series (as an
> incremental fix).
> - To test a new version of the whole series, please send it directly
> to syzbot@lists.linux.dev.
> - 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 bfguo@icloud.com bingfangguo@tencent.com cgroups@vger.kernel.org david@fromorbit.com david@kernel.org devnull@kernel.org hannes@cmpxchg.org kasong@tencent.com linux-kernel@vger.kernel.org linux-mm@kvack.org ljs@kernel.org mhocko@kernel.org muchun.song@linux.dev qi.zheng@linux.dev roman.gushchin@linux.dev shakeel.butt@linux.dev weixugc@google.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
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-upstream-moderation" group.
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--
Ⲡⲟⲓⲙⲏⲛ Ⲅⲉⲱⲣⲅⲓⲟⲥ - Pimyn Girgis
Software Engineer
Kernel Dynamic Analysis
pimyn@google.com
^ permalink raw reply [flat|nested] 2+ messages in thread
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2026-08-13 13:24 [moderation/CI] Re: memcg: fix dying memcg pinned by swapped out shmem pages syzbot ci
2026-08-13 13:25 ` Pimyn Girgis
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