Re: [moderation/CI] Re: Fix an imbalanced file ref count in the mmap syscall

#syz upstream


On Sat, Jul 18, 2026 at 7:45 PM syzbot ci
<[email protected]> wrote:
>
> syzbot ci has tested the following series
>
> [v1] Fix an imbalanced file ref count in the mmap syscall
> https://lore.kernel.org/all/[email protected]
> * [PATCH] mm/vma: fix imbalanced file reference count, properly abort mmap_prepare
>
> and found the following issue:
> WARNING in tear_down_vmas
>
> Full report is available here:
> https://ci.syzbot.org/series/63d42f9f-f249-4678-8916-5464a15accd6
>
> ***
>
> WARNING in tear_down_vmas
>
> tree:      mm-new
> URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm.git
> base:      3827fe994db98623a5a619a72f15f57bf8274deb
> 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/f57e989a-6273-4413-b35d-20dab5a41e92/config
> syz repro: https://ci.syzbot.org/findings/8f36751f-0976-460a-b5ab-de97c9074c0a/syz_repro
>
> ------------[ cut here ]------------
> !vma_is_attached(vma)
> WARNING: ./include/linux/mmap_lock.h:435 at vma_assert_attached include/linux/mmap_lock.h:435 [inline], CPU#0: syz.2.19/5813
> WARNING: ./include/linux/mmap_lock.h:435 at vma_mark_detached include/linux/mmap_lock.h:455 [inline], CPU#0: syz.2.19/5813
> WARNING: ./include/linux/mmap_lock.h:435 at tear_down_vmas+0x381/0x520 mm/mmap.c:1261, CPU#0: syz.2.19/5813
> Modules linked in:
> CPU: 0 UID: 0 PID: 5813 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:vma_assert_attached include/linux/mmap_lock.h:435 [inline]
> RIP: 0010:vma_mark_detached include/linux/mmap_lock.h:455 [inline]
> RIP: 0010:tear_down_vmas+0x381/0x520 mm/mmap.c:1261
> Code: 48 89 df e8 01 46 16 00 48 8b 44 24 18 48 39 03 0f 87 e0 00 00 00 e8 ce a8 a8 ff ff 44 24 04 e9 9a fd ff ff e8 c0 a8 a8 ff 90 <0f> 0b 90 e9 2c ff ff ff e8 b2 a8 a8 ff 90 0f 0b 90 e9 94 fe ff ff
> RSP: 0018:ffffc90003cdf7e0 EFLAGS: 00010293
> RAX: ffffffff821dbb90 RBX: ffff888115e14b40 RCX: ffff888171f9bb80
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc90003cdf920 R08: ffff888115e14b43 R09: 1ffff11022bc2968
> R10: dffffc0000000000 R11: ffffed1022bc2969 R12: ffff888115e14a80
> R13: 0000000000000001 R14: 0000000000000000 R15: dffffc0000000000
> FS:  00007f15b88e36c0(0000) GS:ffff88818dc1c000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f9033eab095 CR3: 0000000173ace000 CR4: 00000000000006f0
> Call Trace:
>  <TASK>
>  exit_mmap+0x4ca/0x9f0 mm/mmap.c:1320
>  __mmput+0x118/0x420 kernel/fork.c:1187
>  exit_mm+0x221/0x2d0 kernel/exit.c:610
>  do_exit+0x6cd/0x2360 kernel/exit.c:992
>  do_group_exit+0x22d/0x2f0 kernel/exit.c:1147
>  get_signal+0x121b/0x12c0 kernel/signal.c:3038
>  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: 0033:0x7f15b799ce59
> Code: Unable to access opcode bytes at 0x7f15b799ce2f.
> RSP: 002b:00007f15b88e30e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: fffffffffffffe00 RBX: 00007f15b7c15fa8 RCX: 00007f15b799ce59
> RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f15b7c15fa8
> RBP: 00007f15b7c15fa0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007f15b7c16038 R14: 00007ffe1b61d9f0 R15: 00007ffe1b61dad8
>  </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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-- 
Ⲡⲟⲓⲙⲏⲛ Ⲅⲉⲱⲣⲅⲓⲟⲥ - Pimyn Girgis
Software Engineer
Kernel Dynamic Analysis
[email protected]