From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-110.freemail.mail.aliyun.com (out30-110.freemail.mail.aliyun.com [115.124.30.110]) (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 CACD31B960 for ; Tue, 5 Aug 2025 06:41:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.110 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754376091; cv=none; b=g1065dilmgID5wMeFDvCGu4UFyhDF7JfHtTCLjjHeeHWWigY+XNhkoPTcRMCV55iTlsl6WPBOxKpUEgo/WcPFHCeSX/+DuUwhQCYKqRo5uBoaDm5DHejenFCOLbg4x+0RmFxpVUQFb9bfs808/Fym9KGkZDoTwaiEmqpowuNcck= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754376091; c=relaxed/simple; bh=QzygLQFMu2kTxxlR2qMgnqwBcyPqL2BCfiJuwFwquV4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sVv42/qppqcgCJl3HvIjdtfCYsVr1Ni6YSfWByPAu84FB/QRLEcxpj1C3GYBBqDpvQ3X4gLo0SWVh0t5+74CMRts/LyCCItXYyYJ5bVvOWAmw9C4I1BCq86pCJHpEkQeDEcDwaUU1CKipm8Xv2c8Q0njEEc1F1O9x4Y7jC5SOlo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=sIE1xJZ9; arc=none smtp.client-ip=115.124.30.110 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="sIE1xJZ9" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1754376085; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=iKwb3jyiyyLlRq/hzHJCa8IJJVZNalYmdaLHaPwmwrU=; b=sIE1xJZ9CIWW6fXKGycIeABlUbx7mE540ro2p3S8r9ZNkXEbOJ7vaE9vGrxwqYayyNYOW7tYlUt6T9l6Ud9msqBEJLjW55pBc/S925BTqSP3cDTUqiTRrRrv6vflZdz0NI7Y5TUa/CM2ULcoLQ1U60rc9sBaOPqWkEY3mjA8q/k= Received: from 30.74.144.114(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0Wl440vN_1754376082 cluster:ay36) by smtp.aliyun-inc.com; Tue, 05 Aug 2025 14:41:23 +0800 Message-ID: <721c093c-a54a-4ccc-b784-e3634a8c2278@linux.alibaba.com> Date: Tue, 5 Aug 2025 14:41:22 +0800 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: [PATCH] mm: Fix the race between collapse and PT_RECLAIM under per-vma lock To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Barry Song , "Lai, Yi" , David Hildenbrand , Lorenzo Stoakes , Qi Zheng , Vlastimil Babka , Jann Horn , Suren Baghdasaryan , Lokesh Gidra , Tangquan Zheng , Lance Yang , Zi Yan , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain References: <20250805035447.7958-1-21cnbao@gmail.com> From: Baolin Wang In-Reply-To: <20250805035447.7958-1-21cnbao@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/8/5 11:54, Barry Song wrote: > From: Barry Song > > The check_pmd_still_valid() call during collapse is currently only > protected by the mmap_lock in write mode, which was sufficient when > pt_reclaim always ran under mmap_lock in read mode. However, since > madvise_dontneed can now execute under a per-VMA lock, this assumption > is no longer valid. As a result, a race condition can occur between > collapse and PT_RECLAIM, potentially leading to a kernel panic. > > [ 38.151897] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] SMP KASI > [ 38.153519] KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f] > [ 38.154605] CPU: 0 UID: 0 PID: 721 Comm: repro Not tainted 6.16.0-next-20250801-next-2025080 #1 PREEMPT(voluntary) > [ 38.155929] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org4 > [ 38.157418] RIP: 0010:kasan_byte_accessible+0x15/0x30 > [ 38.158125] Code: 03 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 48 b8 00 00 00 00 00 fc0 > [ 38.160461] RSP: 0018:ffff88800feef678 EFLAGS: 00010286 > [ 38.161220] RAX: dffffc0000000000 RBX: 0000000000000001 RCX: 1ffffffff0dde60c > [ 38.162232] RDX: 0000000000000000 RSI: ffffffff85da1e18 RDI: dffffc0000000003 > [ 38.163176] RBP: ffff88800feef698 R08: 0000000000000001 R09: 0000000000000000 > [ 38.164195] R10: 0000000000000000 R11: ffff888016a8ba58 R12: 0000000000000018 > [ 38.165189] R13: 0000000000000018 R14: ffffffff85da1e18 R15: 0000000000000000 > [ 38.166100] FS: 0000000000000000(0000) GS:ffff8880e3b40000(0000) knlGS:0000000000000000 > [ 38.167137] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 38.167891] CR2: 00007f97fadfe504 CR3: 0000000007088005 CR4: 0000000000770ef0 > [ 38.168812] PKRU: 55555554 > [ 38.169275] Call Trace: > [ 38.169647] > [ 38.169975] ? __kasan_check_byte+0x19/0x50 > [ 38.170581] lock_acquire+0xea/0x310 > [ 38.171083] ? rcu_is_watching+0x19/0xc0 > [ 38.171615] ? __sanitizer_cov_trace_const_cmp4+0x1a/0x20 > [ 38.172343] ? __sanitizer_cov_trace_const_cmp8+0x1c/0x30 > [ 38.173130] _raw_spin_lock+0x38/0x50 > [ 38.173707] ? __pte_offset_map_lock+0x1a2/0x3c0 > [ 38.174390] __pte_offset_map_lock+0x1a2/0x3c0 > [ 38.174987] ? __pfx___pte_offset_map_lock+0x10/0x10 > [ 38.175724] ? __pfx_pud_val+0x10/0x10 > [ 38.176308] ? __sanitizer_cov_trace_const_cmp1+0x1e/0x30 > [ 38.177183] unmap_page_range+0xb60/0x43e0 > [ 38.177824] ? __pfx_unmap_page_range+0x10/0x10 > [ 38.178485] ? mas_next_slot+0x133a/0x1a50 > [ 38.179079] unmap_single_vma.constprop.0+0x15b/0x250 > [ 38.179830] unmap_vmas+0x1fa/0x460 > [ 38.180373] ? __pfx_unmap_vmas+0x10/0x10 > [ 38.180994] ? __sanitizer_cov_trace_const_cmp4+0x1a/0x20 > [ 38.181877] exit_mmap+0x1a2/0xb40 > [ 38.182396] ? lock_release+0x14f/0x2c0 > [ 38.182929] ? __pfx_exit_mmap+0x10/0x10 > [ 38.183474] ? __pfx___mutex_unlock_slowpath+0x10/0x10 > [ 38.184188] ? mutex_unlock+0x16/0x20 > [ 38.184704] mmput+0x132/0x370 > [ 38.185208] do_exit+0x7e7/0x28c0 > [ 38.185682] ? __this_cpu_preempt_check+0x21/0x30 > [ 38.186328] ? do_group_exit+0x1d8/0x2c0 > [ 38.186873] ? __pfx_do_exit+0x10/0x10 > [ 38.187401] ? __this_cpu_preempt_check+0x21/0x30 > [ 38.188036] ? _raw_spin_unlock_irq+0x2c/0x60 > [ 38.188634] ? lockdep_hardirqs_on+0x89/0x110 > [ 38.189313] do_group_exit+0xe4/0x2c0 > [ 38.189831] __x64_sys_exit_group+0x4d/0x60 > [ 38.190413] x64_sys_call+0x2174/0x2180 > [ 38.190935] do_syscall_64+0x6d/0x2e0 > [ 38.191449] entry_SYSCALL_64_after_hwframe+0x76/0x7e > > This patch moves the vma_start_write() call to precede > check_pmd_still_valid(), ensuring that the check is also properly > protected by the per-VMA lock. > > Fixes: a6fde7add78d ("mm: use per_vma lock for MADV_DONTNEED") > Tested-by: "Lai, Yi" > Reported-by: "Lai, Yi" > Closes: https://lore.kernel.org/all/aJAFrYfyzGpbm+0m@ly-workstation/ > Cc: David Hildenbrand > Cc: Lorenzo Stoakes > Cc: Qi Zheng > Cc: Vlastimil Babka > Cc: Jann Horn > Cc: Suren Baghdasaryan > Cc: Lokesh Gidra > Cc: Tangquan Zheng > Cc: Lance Yang > Cc: Zi Yan > Cc: Baolin Wang > Cc: Liam R. Howlett > Cc: Nico Pache > Cc: Ryan Roberts > Cc: Dev Jain > Signed-off-by: Barry Song > --- LGTM. Reviewed-by: Baolin Wang