syzbot


WARNING in page_counter_uncharge (2)

Status: upstream: reported C repro on 2026/03/28 05:14
Subsystems: cgroups mm
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+226c1f947186f8fef796@syzkaller.appspotmail.com
Fix commit: 15807d0ddde3 mm/hugetlb: fix hugetlb cgroup rsvd charge/uncharge mismatch
Patched on: [ci-qemu-gce-upstream-auto ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb], missing on: [ci-qemu-native-arm64-kvm]
First crash: 94d, last: 13d
Cause bisection: failed (error log, bisect log)
  
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
610b2897-8232-4589-89ab-943f1f5712d2 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in page_counter_uncharge (2) 2026/05/24 08:04 2026/05/24 08:04 2026/05/24 09:13 c69befb30ac10e158cc9d1557b508ee3f0eca1de

			
		
Discussions (2)
Title Replies (including bot) Last reply
[PATCH] mm/hugetlb: fix hugetlb cgroup rsvd charge/uncharge mismatch 4 (4) 2026/04/26 03:47
[syzbot] [mm?] [cgroups?] WARNING in page_counter_uncharge (2) 1 (3) 2026/03/28 06:09
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream WARNING in page_counter_uncharge cgroups mm -1 C done done 2 1642d 1642d 20/29 fixed on 2022/03/08 16:11
linux-6.1 WARNING in page_counter_uncharge origin:lts-only -1 C error 3 174d 210d 0/3 upstream: reported C repro on 2025/12/01 06:16
Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/05/02 06:34 47m retest repro net report log
2026/05/02 06:34 35m retest repro net report log
2026/03/28 06:09 33m kartikey406@gmail.com patch net OK log

Sample crash report:
------------[ cut here ]------------
page_counter underflow: -512 nr_pages=512
WARNING: mm/page_counter.c:60 at page_counter_cancel mm/page_counter.c:60 [inline], CPU#2: syz.3.2707/14164
WARNING: mm/page_counter.c:60 at page_counter_uncharge+0x140/0x1b0 mm/page_counter.c:184, CPU#2: syz.3.2707/14164
Modules linked in:
CPU: 2 UID: 0 PID: 14164 Comm: syz.3.2707 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:page_counter_cancel mm/page_counter.c:60 [inline]
RIP: 0010:page_counter_uncharge+0x147/0x1b0 mm/page_counter.c:184
Code: 2f b8 8a ff 48 83 c4 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc e8 17 b8 8a ff 48 8d 3d 30 0e 60 0e 48 8b 14 24 48 89 ee <67> 48 0f b9 3a be 08 00 00 00 48 89 df e8 d7 b3 f8 ff 48 89 da 48
RSP: 0018:ffffc9000ddef3a0 EFLAGS: 00010093
RAX: 0000000000000000 RBX: ffff88803693f380 RCX: ffffffff827e8c38
RDX: 0000000000000200 RSI: fffffffffffffe00 RDI: ffffffff90de9b00
RBP: fffffffffffffe00 R08: 0000000000000007 R09: 0000000000000000
R10: fffffffffffffe00 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000200 R14: 0000000000000001 R15: 00000000000000f4
FS:  0000000000000000(0000) GS:ffff8880d655f000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb2f22beff8 CR3: 000000000e596000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 __hugetlb_cgroup_uncharge_folio.part.0+0x238/0x620 mm/hugetlb_cgroup.c:354
 __hugetlb_cgroup_uncharge_folio include/linux/hugetlb_cgroup.h:105 [inline]
 hugetlb_cgroup_uncharge_folio_rsvd+0x2e/0x40 mm/hugetlb_cgroup.c:382
 free_huge_folio+0x6cc/0xce0 mm/hugetlb.c:1729
 folios_put_refs+0x6a6/0xa90 mm/swap.c:989
 folio_batch_release include/linux/folio_batch.h:101 [inline]
 remove_inode_hugepages+0x682/0x1090 fs/hugetlbfs/inode.c:582
 hugetlbfs_evict_inode+0x8b/0x250 fs/hugetlbfs/inode.c:597
 evict+0x3c2/0xad0 fs/inode.c:828
 iput_final fs/inode.c:2022 [inline]
 iput.part.0+0x989/0x1050 fs/inode.c:2071
 iput+0x35/0x40 fs/inode.c:2037
 dentry_unlink_inode+0x284/0x470 fs/dcache.c:479
 dentry_kill+0x25d/0xc20 fs/dcache.c:826
 finish_dput fs/dcache.c:1001 [inline]
 dput.part.0+0xd7/0x240 fs/dcache.c:1042
 dput+0x1f/0x30 fs/dcache.c:1037
 __fput+0x519/0xb50 fs/file_table.c:520
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x951/0x2ae0 kernel/exit.c:1004
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1147
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3038
 arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x139/0x6f0 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+0x666/0x870 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7a2eb9ce59
Code: Unable to access opcode bytes at 0x7f7a2eb9ce2f.
RSP: 002b:00007f7a2f9a40e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f7a2ee15fa8 RCX: 00007f7a2eb9ce59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f7a2ee15fa8
RBP: 00007f7a2ee15fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a2ee16038 R14: 00007ffc6d42d140 R15: 00007ffc6d42d228
 </TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
   0:	8a ff                	mov    %bh,%bh
   2:	48 83 c4 10          	add    $0x10,%rsp
   6:	5b                   	pop    %rbx
   7:	5d                   	pop    %rbp
   8:	41 5c                	pop    %r12
   a:	41 5d                	pop    %r13
   c:	41 5e                	pop    %r14
   e:	41 5f                	pop    %r15
  10:	c3                   	ret
  11:	cc                   	int3
  12:	cc                   	int3
  13:	cc                   	int3
  14:	cc                   	int3
  15:	e8 17 b8 8a ff       	call   0xff8ab831
  1a:	48 8d 3d 30 0e 60 0e 	lea    0xe600e30(%rip),%rdi        # 0xe600e51
  21:	48 8b 14 24          	mov    (%rsp),%rdx
  25:	48 89 ee             	mov    %rbp,%rsi
* 28:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2d:	be 08 00 00 00       	mov    $0x8,%esi
  32:	48 89 df             	mov    %rbx,%rdi
  35:	e8 d7 b3 f8 ff       	call   0xfff8b411
  3a:	48 89 da             	mov    %rbx,%rdx
  3d:	48                   	rex.W

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/16 12:47 upstream b1cbabe84ca1 a3998659 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in page_counter_uncharge
2026/06/16 08:05 upstream 0e0611827f33 50bb0618 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in page_counter_uncharge
2026/03/28 01:36 net 5597dd284ff8 74a13a23 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in page_counter_uncharge
2026/03/27 21:51 net 5597dd284ff8 74a13a23 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in page_counter_uncharge
2026/06/12 21:31 net-next f6033078a9e6 1d2f3589 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce WARNING in page_counter_uncharge
2026/04/16 06:23 net 1f5ffc672165 df15c5f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in page_counter_uncharge
2026/04/15 05:21 net b9d8b856689d e2e976a8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in page_counter_uncharge
2026/04/04 11:20 net 1979645e1842 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in page_counter_uncharge
2026/03/28 22:49 net dc9e9d61e301 356bdfc9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in page_counter_uncharge
2026/03/27 20:27 net 5597dd284ff8 74a13a23 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce WARNING in page_counter_uncharge
* Struck through repros no longer work on HEAD.