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 73DE33C660A; Wed, 11 Mar 2026 09:27:48 +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=1773221268; cv=none; b=qKcrT7EuVUpUwcyQqJHy+KIME3tfHZMiSHKsKakOstKVbsmW+JQfYikpPv8Im8EB8KsVcXWr5ljo1f+TPE/p3CvceechKIgUmNLkrJEmXnhnkPO4H0tpMGN1nGm5dnzqti35IdyuFeMqAbVqV3DjoPCpG8e6tpR49/n949bGUQ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773221268; c=relaxed/simple; bh=38Kfamljv28cBObN05dXdaZiATQnnkS/kBzTQ5TLL1Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AKRmlEIYtS8NtBRepQWRAVntW9OzyyfigTF25zk11Thh0gnFP+riJ4bsZWXMhY5Dqf7AHqttVP46XGNofRJng9X1SNYSk7BsdP0BAx/Q/nferF2ZllhS9zZBZOHsbVDp9tPfVsAzTqKaZnYWj6uXCiadMfon0uuRlSygThhSQhQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lOT08OHr; 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="lOT08OHr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35A00C4CEF7; Wed, 11 Mar 2026 09:27:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773221267; bh=38Kfamljv28cBObN05dXdaZiATQnnkS/kBzTQ5TLL1Y=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=lOT08OHrMue36scSLTL0e9RF/OSCvZjnBMLsJurkH25A0NJP5oJ89eRBo2ThNepfb 2J0cbDmVqBBN/dTEs6CcBGbbRTNDsEadHBqzPNtd09oJSJlvUfKBR5CBfPhDBfxJyi jztDyxXqby0IfmH/WbdyGnW/DSYaIPOgu55stBcg67nqegg1bhSGLSaqkURdjQi7PK viunoEf7ue2jlwLinMG148zHSZQ3XELz68GZsb4cz/yqGRwf9Pt8EbH/mATXTpqrnv ldOsmG3xpZJ7oAZOQ0phAuT6GXtBDv57SkMCC3cQ4NL7UZh5I3kN7RngfW0MAi/99S lT55x0fi+eOtA== Message-ID: Date: Wed, 11 Mar 2026 10:27:43 +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: [PATCH v2 1/2] mm: prevent droppable mappings from being locked To: Anthony Yznaga , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: akpm@linux-foundation.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jannh@google.com, pfalcato@suse.de, Jason@zx2c4.com, shuah@kernel.org References: <20260310155821.17869-1-anthony.yznaga@oracle.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 3/10/26 16:58, Anthony Yznaga wrote: > Droppable mappings must not be lockable. There is a check for VMAs with > VM_DROPPABLE set in mlock_fixup() along with checks for other types of > unlockable VMAs which ensures this when calling mlock()/mlock2(). > > For mlockall(MCL_FUTURE), the check for unlockable VMAs is different. > In apply_mlockall_flags(), if the flags parameter has MCL_FUTURE set, the > current task's mm's default VMA flag field mm->def_flags has VM_LOCKED > applied to it. VM_LOCKONFAULT is also applied if MCL_ONFAULT is also set. > When these flags are set as default in this manner they are cleared in > __mmap_complete() for new mappings that do not support mlock. A check for > VM_DROPPABLE in __mmap_complete() is missing resulting in droppable > mappings created with VM_LOCKED set. To fix this and reduce that chance of > similar bugs in the future, introduce and use vma_supports_mlock(). > > Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") Should we Cc: stable? I think we should, to fix mlockall(MCL_FUTURE) behavior. > Suggested-by: David Hildenbrand > Signed-off-by: Anthony Yznaga > --- > v2: > - Implement vma_supports_mlock() instead of vma flags mask (DavidH) > - Add selftests (Lorenzo) > > include/linux/hugetlb_inline.h | 2 +- > mm/internal.h | 10 ++++++++++ > mm/mlock.c | 10 ++++++---- > mm/vma.c | 4 +--- > tools/testing/vma/include/stubs.h | 5 +++++ > 5 files changed, 23 insertions(+), 8 deletions(-) > > diff --git a/include/linux/hugetlb_inline.h b/include/linux/hugetlb_inline.h > index 593f5d4e108b..755281fab23d 100644 > --- a/include/linux/hugetlb_inline.h > +++ b/include/linux/hugetlb_inline.h > @@ -30,7 +30,7 @@ static inline bool is_vma_hugetlb_flags(const vma_flags_t *flags) > > #endif > > -static inline bool is_vm_hugetlb_page(struct vm_area_struct *vma) > +static inline bool is_vm_hugetlb_page(const struct vm_area_struct *vma) > { > return is_vm_hugetlb_flags(vma->vm_flags); > } > diff --git a/mm/internal.h b/mm/internal.h > index cb0af847d7d9..8c67637abcdd 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1218,6 +1218,16 @@ static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf, > } > return fpin; > } > + > +static inline bool vma_supports_mlock(const struct vm_area_struct *vma) > +{ > + if (vma->vm_flags & (VM_SPECIAL | VM_DROPPABLE)) > + return false; > + if (vma_is_dax(vma) || is_vm_hugetlb_page(vma)) > + return false; > + return vma != get_gate_vma(current->mm); As discussed, it would be great to find out whether checking get_gate_vma() makes any sense here. Likely not. :) Acked-by: David Hildenbrand (Arm) -- Cheers, David