From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B79DD3AE6E5 for ; Wed, 25 Feb 2026 13:50:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772027420; cv=none; b=fH84tmakCgGniZgPEutboZcTMW61cxOkK/+GPbj4uGzqNMbKXSoG3M87hexeoNO6lCuGUTzu6Hp7f9Xrgn3yfVIoK7P5eaSGY1GRxFmROkWPIDxTz/Nxycg0kWlG4D+X6FpifJJtq+FCcdsWqXFRqgw6+nUrUx7hcaQwJI2l7nM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772027420; c=relaxed/simple; bh=mevslpoK0ZYqJd8J/tRXskOYzzQGZU6+tC6Xef3xsDo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=etWyNsb2WDbN3YSeVWiOfBzx+H9yGHsV7kkzQzQbAjZ2pAyfGZaAQM/k7Ab1Zw5dssp/LnEufc+zVEImGxksQIi7EV7SHPnWGhGXsIMHSw+QPQR/utTtwAfGiANtVoVjWKZ1T6DYwP3q+SD35q3fuz3WsOuM5+ipzPfCb5RmTyc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oWYj+DK9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oWYj+DK9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6B59C116D0; Wed, 25 Feb 2026 13:50:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772027420; bh=mevslpoK0ZYqJd8J/tRXskOYzzQGZU6+tC6Xef3xsDo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=oWYj+DK9G7R7SbizbH3STLSaU8Lo6I4REPxazn98tRvg8owFxze7IZD0Fgc8ONMao 3iQ/lzXs009ZGq92BwM6afz6LtquWd5BXicLzg6k0Cp0qr1bkgsBG1odk/EyExAqqo ArRnWP7cDxcy0erdcHEX2ZEn+RPjVxLKpxAxGXukSTuMGIzMjCGUwJNDC6Ip8SH50/ MYBGLV+9X+w0/g5AMlJDGCSqYKCNzpGzR52mzkVZOCM6k8F+k+DRf/CjRLGDowEsrp q+RNgtkqGfvwwEdSPAwgfjoNhm3LSQraEc/DG8VFjUrBXGE/rAUY3/3SlVOYdwqCaN Y8Hq6uOXTl3dg== Message-ID: <24cbde8e-53b1-48bb-b44d-2b4bdc674d55@kernel.org> Date: Wed, 25 Feb 2026 14:50:16 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: VM_BUG_ON_VMA in split_huge_pmd_locked: huge PMD doesn't cover full VMA range To: Sasha Levin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Lorenzo Stoakes , Andrew Morton , Hugh Dickins , Zi Yan , Gavin Guo References: From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 2/25/26 14:43, Sasha Levin wrote: > Hi, > > I've been playing around with improvements to syzkaller locally, and hit > the > following crash on v7.0-rc1: > >   vma ffff888109f988c0 start 0000555580cc0000 end 0000555580ce2000 mm > ffff8881048e1780 >   prot 8000000000000025 anon_vma ffff88810b20f100 vm_ops 0000000000000000 >   pgoff 555580cc0 file 0000000000000000 private_data 0000000000000000 >   refcnt 1 >   flags: 0x100073(read|write|mayread|maywrite|mayexec|account) >   ------------[ cut here ]------------ >   kernel BUG at mm/huge_memory.c:2999! >   Oops: invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI >   CPU: 3 UID: 0 PID: 15162 Comm: syz.7.3120 Tainted: G                 > N  7.0.0-rc1-00001-gc5447a46efed #51 PREEMPT(full) >   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0- > debian-1.17.0-1 04/01/2014 >   RIP: 0010:split_huge_pmd_locked+0x11a0/0x2f80 >   RSP: 0018:ffff888053cc7338 EFLAGS: 00010282 >   RAX: 0000000000000126 RBX: ffff888109f988d0 RCX: 0000000000000000 >   RDX: 0000000000000126 RSI: 0000000000000000 RDI: ffffed100a798e43 >   RBP: 0000555580cc0000 R08: ffffffffa3e62775 R09: 0000000000000001 >   R10: 0000000000000005 R11: 0000000000000000 R12: 0000000000000080 >   R13: 0000000000000000 R14: 0000555580c00000 R15: ffff888109f988c0 >   FS:  0000000000000000(0000) GS:ffff88816f701000(0000) > knlGS:0000000000000000 >   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >   CR2: 00007fe2ac1907a0 CR3: 0000000021c91000 CR4: 0000000000750ef0 >   PKRU: 80000000 >   Call Trace: >    >    __split_huge_pmd+0x201/0x350 >    unmap_page_range+0xa6a/0x3db0 >    unmap_single_vma+0x14b/0x230 >    unmap_vmas+0x28f/0x580 >    exit_mmap+0x203/0xa80 >    __mmput+0x11b/0x540 >    mmput+0x81/0xa0 >    do_exit+0x7b9/0x2c60 >    do_group_exit+0xd5/0x2a0 >    get_signal+0x1fdc/0x2340 >    arch_do_signal_or_restart+0x93/0x790 >    exit_to_user_mode_loop+0x84/0x480 >    do_syscall_64+0x4df/0x700 >    entry_SYSCALL_64_after_hwframe+0x77/0x7f >    >   Kernel panic - not syncing: Fatal exception > > The assertion VM_BUG_ON_VMA(vma->vm_start > haddr, vma) fires at > mm/huge_memory.c:2999 because a huge PMD exists at PMD-aligned address > 0x555580c00000 but the VMA only covers [0x555580cc0000, 0x555580ce2000): > a 136KB region starting 816KB past the PMD base. Do you have a reproducer and would this trigger before v7.0-rc1? Lorenzo did some changes around anon_vma locking recently, maybe related to that. -- Cheers, David