[syzbot] [mm?] WARNING in folio_remove_rmap_ptes

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9094662f6707 Merge tag 'ata-6.19-rc2' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1411f77c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a11e0f726bfb6765
dashboard link: https://syzkaller.appspot.com/bug?extid=b165fc2e11771c66d8ba
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11998b1a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=128cdb1a580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-9094662f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5bec9d32a91c/vmlinux-9094662f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3df82e1a3cec/bzImage-9094662f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b165fc...@syzkaller.appspotmail.com

handle_mm_fault+0x3fe/0xad0 mm/memory.c:6580
do_user_addr_fault+0x60c/0x1370 arch/x86/mm/fault.c:1336
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x64/0xc0 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
------------[ cut here ]------------
WARNING: ./include/linux/rmap.h:462 at __folio_rmap_sanity_checks include/linux/rmap.h:462 [inline], CPU#1: syz.0.18/6090
WARNING: ./include/linux/rmap.h:462 at __folio_remove_rmap mm/rmap.c:1663 [inline], CPU#1: syz.0.18/6090
WARNING: ./include/linux/rmap.h:462 at folio_remove_rmap_ptes+0xc27/0xfb0 mm/rmap.c:1779, CPU#1: syz.0.18/6090
Modules linked in:
CPU: 1 UID: 0 PID: 6090 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__folio_rmap_sanity_checks include/linux/rmap.h:462 [inline]
RIP: 0010:__folio_remove_rmap mm/rmap.c:1663 [inline]
RIP: 0010:folio_remove_rmap_ptes+0xc27/0xfb0 mm/rmap.c:1779
Code: 00 e9 49 f4 ff ff e8 a8 35 aa ff e8 c3 55 17 ff e9 98 fc ff ff e8 99 35 aa ff 48 c7 c6 80 b7 9c 8b 4c 89 e7 e8 8a 12 f5 ff 90 <0f> 0b 90 e9 5a f6 ff ff e8 7c 35 aa ff 48 8b 54 24 10 48 b8 00 00
RSP: 0018:ffffc90003f5f260 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffea0001417f80 RCX: ffffc90003f5f144
RDX: ffff88803368c980 RSI: ffffffff8214b106 RDI: ffff88803368ce04
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: ffff88803368d4b0 R12: ffffea0001417f80
R13: ffff888030c90500 R14: 0000000000000000 R15: ffff888012660660
FS: 00007f98fd3fe6c0(0000) GS:ffff8880d69f5000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f98fd3ddd58 CR3: 000000003661c000 CR4: 0000000000352ef0
Call Trace:
<TASK>
zap_present_folio_ptes mm/memory.c:1650 [inline]
zap_present_ptes mm/memory.c:1708 [inline]
do_zap_pte_range mm/memory.c:1810 [inline]
zap_pte_range mm/memory.c:1854 [inline]
zap_pmd_range mm/memory.c:1946 [inline]
zap_pud_range mm/memory.c:1975 [inline]
zap_p4d_range mm/memory.c:1996 [inline]
unmap_page_range+0x1b7d/0x43c0 mm/memory.c:2017
unmap_single_vma+0x153/0x240 mm/memory.c:2059
unmap_vmas+0x218/0x470 mm/memory.c:2101
vms_clear_ptes+0x419/0x790 mm/vma.c:1231
vms_complete_munmap_vmas+0x1ca/0x970 mm/vma.c:1280
do_vmi_align_munmap+0x446/0x7e0 mm/vma.c:1539
do_vmi_munmap+0x204/0x3e0 mm/vma.c:1587
do_munmap+0xb6/0xf0 mm/mmap.c:1065
mremap_to+0x236/0x450 mm/mremap.c:1378
remap_move mm/mremap.c:1890 [inline]
do_mremap+0x13a8/0x2020 mm/mremap.c:1933
__do_sys_mremap+0x119/0x170 mm/mremap.c:1997
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: 0033:0x7f98fdd8f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f98fd3fe038 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
RAX: ffffffffffffffda RBX: 00007f98fdfe5fa0 RCX: 00007f98fdd8f7c9
RDX: 0000000000004000 RSI: 0000000000004000 RDI: 0000200000ffc000
RBP: 00007f98fde13f91 R08: 0000200000002000 R09: 0000000000000000
R10: 0000000000000007 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f98fdfe6038 R14: 00007f98fdfe5fa0 R15: 00007ffd69c60518
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Hillf Danton]

> Date: Mon, 22 Dec 2025 21:23:17 -0800

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 9094662f6707 Merge tag 'ata-6.19-rc2' of git://git.kernel...
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1411f77c580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=a11e0f726bfb6765
> dashboard link: https://syzkaller.appspot.com/bug?extid=b165fc2e11771c66d8ba
> compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11998b1a580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=128cdb1a580000

#syz test

--- x/include/linux/mm.h
+++ y/include/linux/mm.h
@@ -2626,6 +2626,9 @@ static inline void zap_vma_pages(struct
void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
struct vm_area_struct *start_vma, unsigned long start,
unsigned long end, unsigned long tree_end);
+void lock_unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
+ struct vm_area_struct *start_vma, unsigned long start,
+ unsigned long end, unsigned long tree_end);

struct mmu_notifier_range;

--- x/mm/memory.c
+++ y/mm/memory.c
@@ -2104,7 +2104,31 @@ void unmap_vmas(struct mmu_gather *tlb,
} while (vma && likely(!xa_is_zero(vma)));
mmu_notifier_invalidate_range_end(&range);
}
+void lock_unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
+ struct vm_area_struct *vma, unsigned long start_addr,
+ unsigned long end_addr, unsigned long tree_end)
+{
+ struct mmu_notifier_range range;
+ struct zap_details details = {
+ .zap_flags = ZAP_FLAG_DROP_MARKER | ZAP_FLAG_UNMAP,
+ /* Careful - we need to zap private pages too! */
+ .even_cows = true,
+ };

+ mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm,
+ start_addr, end_addr);
+ mmu_notifier_invalidate_range_start(&range);
+ do {
+ unsigned long start = start_addr;
+ unsigned long end = end_addr;
+ hugetlb_zap_begin(vma, &start, &end);
+ vma_start_write(vma);
+ unmap_single_vma(tlb, vma, start, end, &details);
+ hugetlb_zap_end(vma, &details);
+ vma = mas_find(mas, tree_end - 1);
+ } while (vma && likely(!xa_is_zero(vma)));
+ mmu_notifier_invalidate_range_end(&range);
+}
/**
* zap_page_range_single_batched - remove user pages in a given range
* @tlb: pointer to the caller's struct mmu_gather
--- x/mm/vma.c
+++ y/mm/vma.c
@@ -1228,7 +1228,7 @@ static inline void vms_clear_ptes(struct
mas_set(mas_detach, 1);
tlb_gather_mmu(&tlb, vms->vma->vm_mm);
update_hiwater_rss(vms->vma->vm_mm);
- unmap_vmas(&tlb, mas_detach, vms->vma, vms->start, vms->end,
+ lock_unmap_vmas(&tlb, mas_detach, vms->vma, vms->start, vms->end,
vms->vma_count);

mas_set(mas_detach, 1);
@@ -1271,8 +1271,6 @@ static void vms_complete_munmap_vmas(str
mm = current->mm;
mm->map_count -= vms->vma_count;
mm->locked_vm -= vms->locked_vm;
- if (vms->unlock)
- mmap_write_downgrade(mm);

if (!vms->nr_pages)
return;
@@ -1298,7 +1296,7 @@ static void vms_complete_munmap_vmas(str
vm_unacct_memory(vms->nr_accounted);
validate_mm(mm);
if (vms->unlock)
- mmap_read_unlock(mm);
+ mmap_write_unlock(mm);

__mt_destroy(mas_detach->tree);
}
--

[David Hildenbrand (Red Hat)]

On 12/23/25 06:23, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 9094662f6707 Merge tag 'ata-6.19-rc2' of git://git.kernel...
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1411f77c580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=a11e0f726bfb6765
> dashboard link: https://syzkaller.appspot.com/bug?extid=b165fc2e11771c66d8ba
> compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11998b1a580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=128cdb1a580000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-9094662f.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/5bec9d32a91c/vmlinux-9094662f.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/3df82e1a3cec/bzImage-9094662f.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b165fc...@syzkaller.appspotmail.com
>
> handle_mm_fault+0x3fe/0xad0 mm/memory.c:6580
> do_user_addr_fault+0x60c/0x1370 arch/x86/mm/fault.c:1336
> handle_page_fault arch/x86/mm/fault.c:1476 [inline]
> exc_page_fault+0x64/0xc0 arch/x86/mm/fault.c:1532
> asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
> ------------[ cut here ]------------
> WARNING: ./include/linux/rmap.h:462 at __folio_rmap_sanity_checks include/linux/rmap.h:462 [inline], CPU#1: syz.0.18/6090

IIUC, that's the

if (folio_test_anon(folio) && !folio_test_ksm(folio)) {
...
VM_WARN_ON_FOLIO(atomic_read(&anon_vma->refcount) == 0, folio);
}

Seems to indicate that the anon_vma is no longer alive :/

Fortunately we have a reproducer.

CCing Jann who addded that check "recently".

--
Cheers

David

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in folio_remove_rmap_ptes

arch_do_signal_or_restart+0x8f/0x7e0 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
exit_to_user_mode_loop+0x8c/0x540 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x4ee/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
------------[ cut here ]------------
WARNING: ./include/linux/rmap.h:462 at __folio_rmap_sanity_checks include/linux/rmap.h:462 [inline], CPU#2: syz.0.18/6397
WARNING: ./include/linux/rmap.h:462 at __folio_remove_rmap mm/rmap.c:1663 [inline], CPU#2: syz.0.18/6397
WARNING: ./include/linux/rmap.h:462 at folio_remove_rmap_ptes+0xc27/0xfb0 mm/rmap.c:1779, CPU#2: syz.0.18/6397
Modules linked in:
CPU: 2 UID: 0 PID: 6397 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full)

Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:__folio_rmap_sanity_checks include/linux/rmap.h:462 [inline]
RIP: 0010:__folio_remove_rmap mm/rmap.c:1663 [inline]
RIP: 0010:folio_remove_rmap_ptes+0xc27/0xfb0 mm/rmap.c:1779

Code: 00 e9 49 f4 ff ff e8 98 2f aa ff e8 d3 4f 17 ff e9 98 fc ff ff e8 89 2f aa ff 48 c7 c6 40 b8 9c 8b 4c 89 e7 e8 7a 0c f5 ff 90 <0f> 0b 90 e9 5a f6 ff ff e8 6c 2f aa ff 48 8b 54 24 10 48 b8 00 00
RSP: 0018:ffffc90003d9f248 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffea0001468040 RCX: ffffc90003d9f12c
RDX: ffff888028758000 RSI: ffffffff8214b6f6 RDI: ffff888028758484

RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000

R10: 0000000000000001 R11: ffff888028758b30 R12: ffffea0001468040
R13: ffff88802af7d540 R14: 0000000000000000 R15: ffff888026a0e440
FS: 00007f7003d706c0(0000) GS:ffff8880d6af5000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f7003d6ff98 CR3: 0000000032cdb000 CR4: 0000000000352ef0

Call Trace:
<TASK>
zap_present_folio_ptes mm/memory.c:1650 [inline]
zap_present_ptes mm/memory.c:1708 [inline]
do_zap_pte_range mm/memory.c:1810 [inline]
zap_pte_range mm/memory.c:1854 [inline]
zap_pmd_range mm/memory.c:1946 [inline]
zap_pud_range mm/memory.c:1975 [inline]
zap_p4d_range mm/memory.c:1996 [inline]
unmap_page_range+0x1b7d/0x43c0 mm/memory.c:2017
unmap_single_vma+0x153/0x240 mm/memory.c:2059

lock_unmap_vmas+0x30d/0x600 mm/memory.c:2126
vms_clear_ptes+0x419/0x790 mm/vma.c:1231
vms_complete_munmap_vmas+0x186/0x8f0 mm/vma.c:1278
do_vmi_align_munmap+0x446/0x7e0 mm/vma.c:1537
do_vmi_munmap+0x204/0x3e0 mm/vma.c:1585

do_munmap+0xb6/0xf0 mm/mmap.c:1065
mremap_to+0x236/0x450 mm/mremap.c:1378
remap_move mm/mremap.c:1890 [inline]
do_mremap+0x13a8/0x2020 mm/mremap.c:1933
__do_sys_mremap+0x119/0x170 mm/mremap.c:1997
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: 0033:0x7f7002f8f7c9

Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007f7003d70038 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
RAX: ffffffffffffffda RBX: 00007f70031e5fa0 RCX: 00007f7002f8f7c9

RDX: 0000000000004000 RSI: 0000000000004000 RDI: 0000200000ffc000

RBP: 00007f7003013f91 R08: 0000200000002000 R09: 0000000000000000

R10: 0000000000000007 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f70031e6038 R14: 00007f70031e5fa0 R15: 00007ffc9ec46fc8
</TASK>


Tested on:

commit: b9275466 Merge tag 'dma-mapping-6.19-2025-12-22' of gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1419fb58580000

kernel config: https://syzkaller.appspot.com/x/.config?x=a11e0f726bfb6765
dashboard link: https://syzkaller.appspot.com/bug?extid=b165fc2e11771c66d8ba
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16508b92580000