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From: Shakeel Butt To: David Hildenbrand Cc: Andrii Nakryiko , bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, Yi Lai , pbonzini@redhat.com, seanjc@google.com, tabba@google.com, jackmanb@google.com, yosryahmed@google.com, jannh@google.com, rppt@kernel.org Subject: Re: [PATCH bpf] lib/buildid: handle memfd_secret() files in build_id_parse() Message-ID: References: <20241014235631.1229438-1-andrii@kernel.org> <2rweiiittlxcio6kknwy45wez742mlgjnfdg3tq3xdkmyoq5nn@g7bfoqy4vdwt> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 5ayre8jzr9jenjg4ojoi1zccbikwabdw X-Rspamd-Queue-Id: C6A94180023 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1729182163-39011 X-HE-Meta: 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 kQAEKZXe 5QM3xR+CY8ZkFccy4mtvfaS2hRmrL6dCahSlvMhinMelszu7S8TIPU8oHtomHT9WWq86MtYvMcxsDdR7Hh7fZR91/e6iRkW8ACvDEnkfyH5zun5xY4xPR37csT0OW0PNHjqTijKTEmCVCJ3PrWo9BufwUr9KB652yIZspZP9qggGHG7tGkWAcoogQYxYOF9t5uR0yHmbwFJEhiF6IHRhn8k6TXw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Oct 17, 2024 at 11:17:19AM GMT, David Hildenbrand wrote: > On 16.10.24 20:39, Shakeel Butt wrote: > > Ccing couple more folks who are doing similar work (ASI, guest_memfd) > > > > Folks, what is the generic way to check if a given mapping has folios > > unmapped from kernel address space? > > > Can't we just lookup the mapping and refuse these folios that really > shouldn't be looked at? > > See gup_fast_folio_allowed() where we refuse secretmem_mapping(). That is exactly what this patch is doing. See [1]. The reason I asked this question was because I see parallel efforts related to guest_memfd and ASI are going to unmap folios from direct map. (Yosry already explained ASI is a bit different). We want a more robust and future proof solution. [1] https://lore.kernel.org/all/20241014235631.1229438-1-andrii@kernel.org/ > > > -- > Cheers, > > David / dhildenb >