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Howlett" , Vlastimil Babka , Shakeel Butt , David Hildenbrand , Mike Rapoport , Michal Hocko , Uladzislau Rezki , Toshi Kani , Catalin Marinas , David Carlier , Ryan Roberts , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org, syzbot+fd95a72470f5a44e464c@syzkaller.appspotmail.com Subject: Re: [PATCH 0/2] mm: fix UAF caused by race between ptdump and vmap pgtable freeing Message-ID: References: <20260710-series-vmap-race-fix-v1-0-5b3794c113fe@kernel.org> <8e320b30-9658-4e9f-ac4c-f99dcf855944@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 565FCC0009 X-Stat-Signature: qhdycwwi1pjpp4byk8ygfr5ptim4usfk X-HE-Tag: 1783942674-558085 X-HE-Meta: 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 psLb3tKo YO9u2GHpfZvN8vZy934ctkPb+iKQLa5s56SRTdQ+kR9My50jcQZy6/jgkVOA/sroBwFt3bUi1syR1wcnPN+u+kYuKvQXZxK9VQzsB/5GzMULTN6HuvdIZ2CBxLS4F60VCb7ArIipaT3dm+bhrjL+QvVLiXQCxNrlJCe2xFGss17sr8WxLsT4+8YAEk4NoX2ncUD0p6QoQjZ6XeIExMY5B8GauBlmKwJsOiP9b9bTRPKOXwX5kVTIyVyqp6OARNZEryW8IX1K1lHQ210E43GSvyLHaRirr4O7zqzxE9fzZ0ZEduPKXWsk5kU8teIvAteRr7wqomNJVH7ZDvIEABAnBZPqJcgu5ZwTFaBNmP3e2q4Payven+KqZU1yp5lMZJUexM6nrFtZnQQooLqc8jsoefi561DmxuYRBL4lXqXFPWtzyrAIjzds3em1g0KhdfOt+vMyC+lZlhwk7NPTjiBO3Bw6lfQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Jul 12, 2026 at 09:46:46AM +0100, Lorenzo Stoakes wrote: > On Sun, Jul 12, 2026 at 12:50:08PM +0530, Dev Jain wrote: > > Will Deacon had pushed back on a similar approach: > > https://lore.kernel.org/all/20250530123527.GA30463@willie-the-truck/ > > > > Although now when I read back that thread, it feels more so like my > > incompetency to convince :) because: > > No haha not so, I think more like this stuff is fiddly. Yup, not disputing that this is hard to get right. Conceptually, adding locking purely to deal with a vanishingly rare, debug reader does turn my head but I'm _far_ less concerned about it if it's done in the core code, as is the case here. x86 needs it and we're recently running into related locking issues with the set_memory_*() APIs if we want to collapse the page-table on arm64 [1]. If the overhead is flagged as an issue, we can see if it's worth generalising the static key trick that the second patch reverts but I definitely wouldn't start from that position. Will [1] https://lore.kernel.org/linux-arm-kernel/799181c3-a1a1-4de7-bc6a-576d3282efb0@arm.com/