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b=jIEyu1dv/G4tXeoiWpSNi4nEf3g58BTBHj2mu/oATMIOixTT41BqLjCQxdgDqOlMR dWo1Irhc9Rda6uMgaylO7vhng4jYYp2ncOAl0bMG9Z9Wscn47ydAYWqszHgk8kkwvm jIIeE2kA2LmeaerQl6GOhhAy00f+21223GH6HUC15vORxdsEiCRKFYCWW5i0G9bczv E5aqD6XXBCTyhp4zy8LNf+7lQsDqsk4VhKoxq2mYxVoOAz5iP9ArCF0i3h0FnIQmAJ QktSsW6qGCUJ7X7h8eklysemTHCLn9XpED5QjOdDJWp+TtyksQHMOgjl0o9Bi9QGYd CTikNaGY7gqYA== Message-ID: <2c069fb1-fd23-4e7b-92de-7f4a4eaa4f67@kernel.org> Date: Thu, 12 Mar 2026 09:32:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] mm: prevent droppable mappings from being locked To: anthony.yznaga@oracle.com, "Lorenzo Stoakes (Oracle)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, akpm@linux-foundation.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> <269b1a31-20d1-4451-b4ba-f55a67f27d96@lucifer.local> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: ghsdbjjq5o8koo1zp3xbygmwxj5p5bpe X-Rspam-User: X-Rspamd-Queue-Id: 201D014000E X-Rspamd-Server: rspam12 X-HE-Tag: 1773304358-994510 X-HE-Meta: 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 Q2T3mJpx /AttIpi0K4S8dIZ82YT+EyCdOtP/v9n17KtI7lon5e/r3WnfsZPRS2x8Hb7j3ODojRon4DM5xcirUw4ErKcwRx62EZf8qI/t2Sh2oOA0PcGnY2VFAFvjkzHeAyPU8JJU1BT3WKqxYvlGf2nApzV4f8CRYa67K/+I1dR3BBpDXM8KBcBLuEfXhrbfblglQ+dYKkG3ZG6s/r+AzQM4gJUmSZQ+zPeeR2Gg2fT1PdqSs/LbbXv6Bylv6ntuIPgn11HkXfye4CBJwqphbTV+ulsD0wSYbrQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/12/26 03:16, anthony.yznaga@oracle.com wrote: > > On 3/11/26 3:36 AM, Lorenzo Stoakes (Oracle) wrote: >> On Tue, Mar 10, 2026 at 08:58:20AM -0700, 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") >> We should definitely cc: stable I think. >> >> It might result in some backport pain since it'll probably pre-date the >> __mmap_region() stuff :)) sorry. > > I could add a patch at the beginning that does the cheap fix followed by > this patch. Any backport conflicts should be easy and fast too resolve (if any). No need to uglify our mainline patches :) -- Cheers, David