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Tue, 25 Aug 2026 18:40:01 -0700 (PDT) From: Daehyeon Ko <4ncienth@gmail.com> To: Lorenzo Stoakes Cc: Andrew Morton , Mike Rapoport , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Alexei Starovoitov , Daniel Borkmann , "David S . Miller" , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , James Bottomley , Hagen Paul Pfeifer , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] mm/secretmem: properly account locked pages Date: Wed, 26 Aug 2026 10:39:48 +0900 Message-ID: <20260826013948.1325213-1-4ncienth@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260822-secretmem-accounting-v2-1-fe445a7c6eb1@kernel.org> References: <20260822-secretmem-accounting-v2-1-fe445a7c6eb1@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: ytorsus5455a8jqwd1rgok7tybor6tkp X-Rspamd-Queue-Id: B31281A0008 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1787708403-670265 X-HE-Meta: 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 W53WxKUt TotNhI52wSIwT2XNdfbO1FoinWUBamRJfGyO5JxPH3gPx1AyKHtFKm//AfbZqnZQnfWig0xifo4GCXDE2/g99h8n0PGS3/A9ioOOJOcyHwggOKo9i1YLgStfNH01e6gDaGkRyYC8Q0iCTirKBOTAZ0fgPAhQT9lNNr1JgIAvkiAB38wwOqrWcp1KMeuVCcuzDzGH/HyeXzQG6HdDPVB6mKMlgfCE9FwYHRbc/BkbgJNE4K7+uZ85/G6X8NKlwvwTXSjzkAV+cf0lsOFcvXheScZxpVlERYYQJeRtcBn0DCJUlvB3D3T8BTAFT6OrOHVfd6JZg+1hvWVE+SJwjYy4KjmdJTQA0AlsC1sIH0HbxQjmIZ07u9CYkZ4FT0LefN0k5ZX0Kd42D8biebfSMGnFzgKYthW5Ocnrd2eIRxtvmBIrqBrKVCkKgXZH4dIBgh0f1NH1dSERmRnnWPr2+LejxnddwrzQl9JEbo8/h8UuXU4eg3Lk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Lorenzo, I tested the exact v2 from this Message-ID on its stated base with an x86_64 KASAN kernel. The supplied memfd_secret selftest passed 6/6 in three boots, and my accounting-boundary suite also passed in three boots. I saw no patch-attributable KASAN report, warning, Oops, or panic. A v1/v2 differential also confirms that v2 fixes the CAP_IPC_LOCK creator delegation issue Mike identified: v1: CAP_DELEGATION creator_cap_ipc_lock=1 receiver_uid=2001 receiver_pages=2 v2: CAP_DELEGATION creator_cap_ipc_lock=1 receiver_uid=2001 receiver_pages=1 I have one policy question before adding Tested-by. With a one-page soft and hard RLIMIT_MEMLOCK, a non-root task whose only effective and permitted capability was CAP_IPC_LOCK produced this on v2: CAP_ONLY uid=2002 cap_ipc_lock=1 mlock_two_pages=1 faulted_pages=1 raise_hard_rc=-1 raise_hard_errno=1 Thus ordinary mlock() of two pages succeeded, while only one secretmem page could be faulted. Raising the hard limit failed with EPERM because that requires CAP_SYS_RESOURCE. Is this divergence from ordinary mlock() the intended consequence of removing the CAP_IPC_LOCK exemption for secretmem? I saw the planned selftest split and cleanup in the follow-up discussion. I will retest the revised patch before adding Tested-by. Thanks, Daehyeon