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[209.85.218.51]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5b83bf3b99dsm3800359a12.91.2024.08.04.10.47.40 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 04 Aug 2024 10:47:40 -0700 (PDT) Received: by mail-ej1-f51.google.com with SMTP id a640c23a62f3a-a7a94478a4eso828598066b.1 for ; Sun, 04 Aug 2024 10:47:40 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCU+yUgw3s7VO8ZJWz1olmmjUGUgDvijS5O0vZCqFsZZ5czjmvhnuiMUyi0Cix8Az3gIsGFqEoIMbH439v3rm8TKu94= X-Received: by 2002:a17:907:804:b0:a7a:130e:fb6e with SMTP id a640c23a62f3a-a7dbcc21307mr914595866b.15.1722793659883; Sun, 04 Aug 2024 10:47:39 -0700 (PDT) MIME-Version: 1.0 References: <20240804152327.GA27866@redhat.com> In-Reply-To: <20240804152327.GA27866@redhat.com> From: Linus Torvalds Date: Sun, 4 Aug 2024 10:47:23 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH] piped/ptraced coredump (was: Dump smaller VMAs first in ELF cores) To: Oleg Nesterov Cc: Brian Mak , "Eric W. Biederman" , Kees Cook , Alexander Viro , Christian Brauner , Jan Kara , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: EF13B4001F X-Rspamd-Server: rspam01 X-Stat-Signature: 69gc5ohw45gupdi63uod1iy8j3sdequx X-HE-Tag: 1722793663-389347 X-HE-Meta: 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 YW8Hw6Pt 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 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 Sun, 4 Aug 2024 at 08:23, Oleg Nesterov wrote: > > What do you think? Eww. I really don't like giving the dumper ptrace rights. I think the real limitations of the "dump to pipe" is that it's just being very stupid. Which is fine in the sense that core dumps aren't likely to be a huge priority. But if or when they _are_ a priority, it's not a great model. So I prefer the original patch because it's also small, but it's conceptually much smaller. That said, even that simplified v2 looks a bit excessive to me. Does it really help so much to create a new array of core_vma_metadata pointers - could we not just sort those things in place? Also, honestly, if the issue is core dump truncation, at some point we should just support truncating individual mappings rather than the whole core file anyway. No? Depending on what the major issue is, we might also tweak the heuristics for which vmas get written out. For example, I wouldn't be surprised if there's a fair number of "this read-only private file mapping gets written out because it has been written to" due to runtime linking. And I kind of suspect that in many cases that's not all that interesting. Anyway, I assume that Brian had some specific problem case that triggered this all, and I'd like to know a bit more. Linus