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Thu, 26 Feb 2026 14:02:17 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 26 Feb 2026 15:02:25 +0100 (CET) Date: Thu, 26 Feb 2026 15:02:16 +0100 From: Oleg Nesterov To: Andrei Vagin Cc: Pavel Tikhomirov , Christian Brauner , Shuah Khan , Kees Cook , Andrew Morton , David Hildenbrand , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Jan Kara , Aleksa Sarai , Andrei Vagin , Kirill Tkhai , Alexander Mikhalitsyn , Adrian Reber , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 2/4] pid: check init is created first after idr alloc Message-ID: References: <20260224164852.306583-1-ptikhomirov@virtuozzo.com> <20260224164852.306583-3-ptikhomirov@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-MFC-PROC-ID: kqLrsByJdyLgeVJgSznZKlv4KEwopwFYnNiJ2TEfmuU_1772114547 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Stat-Signature: 4rzhwdrtd5ci3cis9w9myrno4nnj7sdm X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A631BA000C X-HE-Tag: 1772114556-620129 X-HE-Meta: U2FsdGVkX19a9GU53CbPe3jBRyiNF+VQKLrY8YN2tfrplzi5J310jCHR+x3DuEW0ib8ecMGFfNYjb9+4C9ghnocY4VwIgoiP/VGRODPflqmwZAsMyREtp6PBKcZTigC4N07wKbga0h2kwF2KQLl59O7NUnutn4Qj8w/iNoOLgLa6czMMwQal0o6aaK3yxL7p/kbdmBwbXj1IyYWVyVyTL4TvfIZNr3Wv8K9n7Vgdfq4Pbs37O5ZLl8RZzOf0R+ktUNayJCKFX6ehrQXg6SkX7yMz/ILm7aHYYEwnIkX7z1K/96o0RSGlPTZKqHPEcWP/mjpTy0aUCP/uUAmW6z4xEGkVWr0UZOt4H7YmUhJHoR2kFLwH+u3WVcHcfwkA0UTVZr+7dku2kD+eY8XtO2+QmEYVK7nvZx755M5OvC/3N3NHySZvpKjp3sexgYI6uQrPkrpXKotSqhVUCCDeySVobk3NCsJm43N0ee9uo8okQiLH2NkXqTo1kXpRrgsI9P2cRW7y4eFD2PO7YuVN0SCPvq3wAfR/QsANRMtdOD/C0Vpuv7ghftGvryVkOzJTc+mngoGF+x6u5MhvGsTPTLOzdws9M6jgHNnJq69MxIR/94tBLdvmoDiTAuTu/ZkTZObLBq6A8k8W0GrbUg1k1gc6r+v5eaEhKqGMbXWccCuo6DJy9X7C4rBGOgJCvTWolaZnpxuXcdz5kHsyM+TgnWBRr8NGbVX4xOYP9jo3qeGZMcQnm1VMF7c6iNAHbOlF3KudRdmt/+P7Q41yil1cuhmByM+FQ9gOpPBOwXUqZxkQna63K02hastVZjHqEIcTX5bF+Xs3Vv6FvjPO/Tr5DikfPpIJwxEv3xfXefDNbx9OoqyKL0n78emorlH3sEPlWXt6iemoJHo2gQEL/A5RCPTXuYFLuv4z9QEZnsugjej+lXbIelHmjVZ0uM/pQSZVuyvyTBbN/lR9L/ncFWlwJPx Ji89lhci wmwA68M9bdIb6oA4ceEMe0ZAPpvF7kQEkm8tdmIant3l8KcUOOqmZojYAfFrkAdQsLF4Qk+H6494o/QXIxEZcvu1Zz5CZCXFCZfvUfpk94e5OJRR6PJPVke88uz+Q3leYh9Ywqs7LLoB9rKbFZxQ3maKWaKWNErJJrEA1fTOPrPcqsrr82+qLkyAISaGXT4Z46UJnUF7o7SlnzmwyPPM3zkAkp0Qpdu/Tcj4PeCK4Jf8ZJqO1I6tbkPGBNFFgi/Q8EflF81tdOj0stsNpIWKUWcPdUqr/C5NQKYZVObzzr0SKgT3ncnuPjCsLgyQFmh+Xdxo78YSqqmyjyjkuh0TY/7Fswr75KK7UhPjF Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 02/26, Oleg Nesterov wrote: > > Now that I look at this code again... Why do we bother to check > "pid_allocated & PIDNS_ADDING" at all? copy_process() does > > /* Don't start children in a dying pid namespace */ > if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { > retval = -ENOMEM; > goto bad_fork_core_free; > } > > I am going to send the patch which removes this check from alloc_pid... > Need to recheck. No, we can't remove either of these 2 checks... This probably deserves another comment in alloc_pid(). Oleg.