[syzbot] WARNING in page_counter_cancel (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cb71b93c2dc3 Add linux-next specific files for 20220628
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15583826080000
kernel config: https://syzkaller.appspot.com/x/.config?x=badbc1adb2d582eb
dashboard link: https://syzkaller.appspot.com/bug?extid=28eb226ee1d37f08087a
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12222b9a080000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1560ab8c080000

The issue was bisected to:

commit 2ee236fe53a8e2ab54679c74e8a1fb77e55b29bb
Author: Liam R. Howlett <Liam.H...@Oracle.com>
Date: Tue Jun 21 20:46:53 2022 +0000

mm: start tracking VMAs with maple tree

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10b5b252080000
final oops: https://syzkaller.appspot.com/x/report.txt?x=12b5b252080000
console output: https://syzkaller.appspot.com/x/log.txt?x=14b5b252080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+28eb22...@syzkaller.appspotmail.com
Fixes: 2ee236fe53a8 ("mm: start tracking VMAs with maple tree")

------------[ cut here ]------------
page_counter underflow: -512 nr_pages=1536
WARNING: CPU: 0 PID: 3608 at mm/page_counter.c:56 page_counter_cancel+0xcf/0xe0 mm/page_counter.c:56
Modules linked in:
CPU: 0 PID: 3608 Comm: syz-executor428 Not tainted 5.19.0-rc4-next-20220628-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
RIP: 0010:page_counter_cancel+0xcf/0xe0 mm/page_counter.c:56
Code: c7 04 24 00 00 00 00 45 31 f6 eb 97 e8 2a 36 ae ff 4c 89 ea 48 89 ee 48 c7 c7 a0 55 da 89 c6 05 26 90 db 0b 01 e8 bb bb 67 07 <0f> 0b eb a8 4c 89 e7 e8 65 3b fa ff eb c7 0f 1f 00 41 56 41 55 49
RSP: 0018:ffffc9000302fb28 EFLAGS: 00010282
RAX: 0000000000000000 RBX: ffff888140159268 RCX: 0000000000000000
RDX: ffff88801ea81d40 RSI: ffffffff81610608 RDI: fffff52000605f57
RBP: fffffffffffffe00 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000001 R12: ffff888140159268
R13: 0000000000000600 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb2ef03c290 CR3: 000000002234d000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
page_counter_uncharge+0x2e/0x60 mm/page_counter.c:159
hugetlb_cgroup_uncharge_counter+0xcc/0x3d0 mm/hugetlb_cgroup.c:432
hugetlb_vm_op_close+0x424/0x6b0 mm/hugetlb.c:4598
remove_vma+0x81/0x130 mm/mmap.c:187
exit_mmap+0x288/0x720 mm/mmap.c:3222
__mmput+0x128/0x4c0 kernel/fork.c:1180
mmput+0x5c/0x70 kernel/fork.c:1201
exit_mm kernel/exit.c:510 [inline]
do_exit+0xa09/0x29f0 kernel/exit.c:782
do_group_exit+0xd2/0x2f0 kernel/exit.c:925
__do_sys_exit_group kernel/exit.c:936 [inline]
__se_sys_exit_group kernel/exit.c:934 [inline]
__x64_sys_exit_group+0x3a/0x50 kernel/exit.c:934
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7fb2eefc6d39
Code: Unable to access opcode bytes at RIP 0x7fb2eefc6d0f.
RSP: 002b:00007ffc35614978 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fb2ef03b3f0 RCX: 00007fb2eefc6d39
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffffffffffc0 R09: 0000000000000003
R10: 0000000020000000 R11: 0000000000000246 R12: 00007fb2ef03b3f0
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
</TASK>


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Liam Howlett]

* syzbot <syzbot+28eb22...@syzkaller.appspotmail.com> [220718 03:45]:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: cb71b93c2dc3 Add linux-next specific files for 20220628
> git tree: linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=15583826080000
> kernel config: https://syzkaller.appspot.com/x/.config?x=badbc1adb2d582eb
> dashboard link: https://syzkaller.appspot.com/bug?extid=28eb226ee1d37f08087a
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12222b9a080000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1560ab8c080000
>
> The issue was bisected to:
>
> commit 2ee236fe53a8e2ab54679c74e8a1fb77e55b29bb
> Author: Liam R. Howlett <Liam.H...@Oracle.com>
> Date: Tue Jun 21 20:46:53 2022 +0000
>
> mm: start tracking VMAs with maple tree
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10b5b252080000
> final oops: https://syzkaller.appspot.com/x/report.txt?x=12b5b252080000
> console output: https://syzkaller.appspot.com/x/log.txt?x=14b5b252080000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+28eb22...@syzkaller.appspotmail.com
> Fixes: 2ee236fe53a8 ("mm: start tracking VMAs with maple tree")
>

Thank you. Yes, it looks like failing the allocation after
vma_adjust_trans_huge() is not working out here. What happens is a
split fails to vm_adjust, so we enter the __split_vm() error code path
which calls vm_ops->close(). The account for the hughtlb is actually
done in the close() operation. What I can do is to avoid accounting by
setting vm_start = vm_end, and vm_pgoff = 0. This way, the accounting
will charge 0 as apposed to removing the vma that was never added.

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.