Re: [moderation/CI] Re: mm: rework anon_vma and remove anon_vma_chain

#syz upstream

On Tue, Jul 7, 2026 at 8:30 PM syzbot ci
<[email protected]> wrote:
>
> syzbot ci has tested the following series
>
> [v2] mm: rework anon_vma and remove anon_vma_chain
> https://lore.kernel.org/all/[email protected]
> * [RFC PATCH v2 01/13] mm: add CONFIG_ANON_VMA_FRACTAL
> * [RFC PATCH v2 02/13] mm: implement helpers for ANON_VMA_FRACTAL
> * [RFC PATCH v2 03/13] mm: implement __anon_node_prepare for ANON_VMA_FRACTAL
> * [RFC PATCH v2 04/13] mm: implement anon_node_clone for ANON_VMA_FRACTAL
> * [RFC PATCH v2 05/13] mm: implement anon_node_fork_with_prev for ANON_VMA_FRACTAL
> * [RFC PATCH v2 06/13] mm: implement unlink_anon_nodes for ANON_VMA_FRACTAL
> * [RFC PATCH v2 07/13] mm: handle rmap_base changes for ANON_VMA_FRACTAL
> * [RFC PATCH v2 08/13] mm: implement anonymous folio rmap for ANON_VMA_FRACTAL
> * [RFC PATCH v2 09/13] mm: prepare anon_node replacement for ANON_VMA_FRACTAL
> * [RFC PATCH v2 10/13] mm: replace anon_vma with anon_node for ANON_VMA_FRACTAL
> * [RFC PATCH v2 11/13] mm: optimize rmap for ANON_VMA_FRACTAL with PVL
> * [RFC PATCH v2 12/13] mm: shared semaphores for ANON_VMA_FRACTAL
> * [RFC PATCH v2 13/13] mm: Enable CONFIG_ANON_VMA_FRACTAL by default
>
> and found the following issue:
> WARNING: bad unlock balance in exc_page_fault
>
> Full report is available here:
> https://ci.syzbot.org/series/39466cf1-707b-420e-8f1e-11735bea6c66
>
> ***
>
> WARNING: bad unlock balance in exc_page_fault
>
> tree:      mm-new
> URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm.git
> base:      8ff49efd1cf18086320f3b43d1bd483c0b9e7e58
> arch:      amd64
> compiler:  Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
> config:    https://ci.syzbot.org/builds/c3a229e4-b949-4889-b309-dbdd1fadd95f/config
> syz repro: https://ci.syzbot.org/findings/29b52ad4-b463-41da-877c-4138356e3960/syz_repro
>
> =====================================
> WARNING: bad unlock balance detected!
> syzkaller #0 Not tainted
> -------------------------------------
> sshd/5593 is trying to release lock (vm_lock) at:
> [<ffffffff8bb5032a>] handle_page_fault arch/x86/mm/fault.c:1483 [inline]
> [<ffffffff8bb5032a>] exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
> but there are no more locks to release!
>
> other info that might help us debug this:
> no locks held by sshd/5593.
>
> stack backtrace:
> CPU: 1 UID: 0 PID: 5593 Comm: sshd 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
>  print_unlock_imbalance_bug+0xdc/0xf0 kernel/locking/lockdep.c:5298
>  __lock_release kernel/locking/lockdep.c:5527 [inline]
>  lock_release+0x1f1/0x3c0 kernel/locking/lockdep.c:5889
>  vma_refcount_put include/linux/mmap_lock.h:216 [inline]
>  vma_end_read include/linux/mmap_lock.h:264 [inline]
>  do_user_addr_fault+0xab0/0x1340 arch/x86/mm/fault.c:1345
>  handle_page_fault arch/x86/mm/fault.c:1483 [inline]
>  exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1536
>  asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:595
> RIP: 0033:0x5583206de68b
> Code: 04 25 28 00 00 00 48 89 44 24 08 31 c0 48 89 e2 e8 8c 5b ff ff 85 c0 78 13 31 c0 4d 85 e4 74 0c 48 8b 3c 24 48 89 de 4c 89 e1 <f3> a4 48 8b 54 24 08 64 48 2b 14 25 28 00 00 00 74 05 e8 5e 17 fc
> RSP: 002b:00007fff02a37e60 EFLAGS: 00010206
> RAX: 0000000000000000 RBX: 000055835a20d6fe RCX: 0000000000008000
> RDX: 0000000000000000 RSI: 000055835a20d6fe RDI: 00007fac5106c010
> RBP: 000055832073df00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000008000
> R13: 000000000000005e R14: 00000000000000b3 R15: 00007fff02a37f88
>  </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: [email protected]
>
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