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imf28.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=r32POjOe; spf=pass (imf28.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773131125; a=rsa-sha256; cv=none; b=2YNbUVVoWlsTYDAdSUqi5AeMQNZnVvuSa/85y+WKQzbOkOpOtk3eJcIGiC3supsZkUzvTO MyYnTJDhn9xoQWsJ9a1pbbk1lCXhX2pSC7OEePpLgeKut4b6ou07lNa+P6mwDSIakdwynb lfguED3p/4t7VqjTryoLeNS0krANLYo= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 2F1CB600AE; Tue, 10 Mar 2026 08:25:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4D579C19423; Tue, 10 Mar 2026 08:25:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773131124; bh=3mkGCn1+SE6g3BjC4GosyHZuWAmHGngGuk1f3nEWOZ0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=r32POjOe0rj5ODQJl17XFaTxfn1KO5JF0+dr/nQ2Tts2YH6vMre+CwtuFtH9oLRly txV0zmknTNme8X1zFgHE5PI8KxGEUm7MF+f/hUgyQY4lZRPeaYduZYjhGrAhoK4UMJ c/sby567r6k8FCJUZ39iOUgKz025M/doaL3azCvfxB2zfn5wX//lTfzns+wItUMmPe 8/mTfv0nKphrYrvkB8NQHEA4HrS+/ppFbhIbUY4CDL8X9zn0lZknEQHQ+vECXKdv3o tDhLowMijFdMDdw2ZIw/QiX2hAyHw5EOvnLO1BWMZIER8TazRL/2mztEtxkDjrL+7W JRFLa/BMc5TdQ== Message-ID: <4becce7a-af3e-4f29-a233-71d90f653daa@kernel.org> Date: Tue, 10 Mar 2026 09:25:17 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: prevent droppable mappings from being locked To: anthony.yznaga@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, 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 References: <20260306204550.8405-1-anthony.yznaga@oracle.com> <7c1db5ef-2457-46ff-ab20-dd4090570fb6@kernel.org> <7c4a45c3-298a-4a72-b551-ec687898b4f3@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: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: B8A94C0005 X-Stat-Signature: 3hke33k7htjx61asuwif5fpa7ygwrugj X-Rspam-User: X-HE-Tag: 1773131125-330065 X-HE-Meta: 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 R7nWP6va 5ZEgWs47ugeHH7Z4yJRa5/FP1pBNKusnT2KjUp4juk11NUZ+/yKWh/8UEoDIVwywXvUrzobO+6CNUj2I0v56EPf/a0mJ6AwDuaewhXHY4bC5uEt5E4sOKJ3KagnyKc89Gvab7vh9GzwWkWX6prg6I3EvtTL3eunfeYHm1Mm8cPCcKE5k0Z5u7jyn6r4m/wPRZ8IPChsfw1l66vUlU6HkFl0reC7v9lrwhQgKChBLYXhCXLJd5RbwBDwZoOVreFI45o1P7vXcZn9bsIraPBfIyfnpYbCOvgf6UxUlfJODd/Mq3GKuJBWotEfy9k9fx1jQw1sPFlyzYrMMPEQjH4FiZJiKA+Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/10/26 03:04, anthony.yznaga@oracle.com wrote: > > On 3/9/26 7:15 AM, David Hildenbrand (Arm) wrote: >> On 3/6/26 21:45, Anthony Yznaga wrote: >>> Mappings created with MAP_DROPPABLE cannot be locked via mlock() due >>> to the check in mlock_fixup(). However, they will be locked indirectly >>> if they are created after mlockall(MCL_FUTURE). >>> >>> Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always >>> lazily freeable mappings") >>> Signed-off-by: Anthony Yznaga >>> --- >>>   include/linux/mm.h | 3 +++ >>>   mm/mlock.c         | 4 ++-- >>>   mm/vma.c           | 2 +- >>>   3 files changed, 6 insertions(+), 3 deletions(-) >>> >>> diff --git a/include/linux/mm.h b/include/linux/mm.h >>> index 5be3d8a8f806..bb830574d112 100644 >>> --- a/include/linux/mm.h >>> +++ b/include/linux/mm.h >>> @@ -574,6 +574,9 @@ enum { >>>   /* This mask represents all the VMA flag bits used by mlock */ >>>   #define VM_LOCKED_MASK    (VM_LOCKED | VM_LOCKONFAULT) >>>   +/* This mask prevents VMAs from being mlock'd */ >>> +#define VM_NO_MLOCK_MASK    (VM_SPECIAL | VM_DROPPABLE) >> Instead of adding that, could we cleanup further by doing something >> like the following? >> >> The usage of "vma->vm_mm" must be double checked, > > This sent me down an interesting rabbit hole since gate_vma->vm_mm is > initialized to NULL. I can't see how the gate VMA could ever be passed > to mlock_fixup() or __mmap_complete() if it's not part of the VMA tree > of an mm and is not mapped through mmap. Right, gate_vma() would be shared across all processes. Wouldn't code like the following be questionable as well? fs/coredump.c: if (vma == get_gate_vma(vma->vm_mm)) mm/vmscan.c: if (vma == get_gate_vma(vma->vm_mm)) I mean, that cannot possibly be true unless I am missing something. There are a couple of other > places in the kernel that assume the gate VMA may be encountered when > iterating VMAs, too. Am I missing something? Happy to clean these up if > it makes sense. Yes, please look into that. As an alternative, we could maybe pass current->mm to get_gate_vma() ... but it'd be best to just clean that up. -- Cheers, David