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Thu, 10 Sep 2026 06:44:41 +0000 X-Mizu-Trace-ID: f6102d5745d8b7b1 X-Migadu-Flow: FLOW_OUT From: Hongfu Li To: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, James.Bottomley@HansenPartnership.com Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Hongfu Li Subject: [PATCH v2] selftests/mm: fix ptrace PEEKDATA check in memfd_secret test Date: Thu, 10 Sep 2026 14:44:15 +0800 Message-ID: <20260910064415.71623-1-hongfu.li@linux.dev> X-Mailer: git-send-email 2.54.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 543hcuszubt5kow1j4nsxto7biyngzmz X-Rspam-User: X-Rspamd-Queue-Id: 55C6840003 X-Rspamd-Server: rspam03 X-HE-Tag: 1789022688-291916 X-HE-Meta: U2FsdGVkX19EFlkmP4tHYU/52fu+/bQ6b+rYYRggBlJK8aaehFCKvlb/VRCmYqXD34Ca2/O5+Hwwb6k6FBuBuOWmxxlKvj6GapiUV6ojKWH/vbX/9YQNuc1rCAtRuyqIowm2XAsn5kWe2tdLjxSj2SeZxiOZJ1ZuantizAICZcj1SPUCS8bqoU5YvnApdBZYRjbOohufc1VWMVcwRgsu5T5D+VsuV6XDtkI5IGAPUEdAr0GKu8XYDoLFxj/zxSg1QbGHYu6ARXMfdM3aPDi2HKpTMiUdstBbgkskB9khpVr/TkewFnT1LLUI+YcZya1Np1vefXqxIAa6aiCfMhizkMc6EtORqvF3+ESQ8ZKkV4tzc0afQAZryV+e2Lmb5ORoyRnHNkpuO7/JIVbB12DHDhPDTiGXJ6Oj28cW0xkT3H+l0H+WrLeepJAtOw9iqzthUIqgPVJNGHQ/epR6swoLioHKaPb0LjCUnKL7T2pm7ZuQ/wmjKvMrSGraLuCSZUeM3jWgk2Nknf/RY3WbGFEAcf2LIqF5LWUB0dljfatmhvgONiRW6UEMGclt98RdiSvdWrhF3IzXGP5j6nSw7uawO8YiHPQHpiLtAKgDCKfgTCiPynmgYTIlh1uJs+ZvWrtMicmGVM4evYX1yKUPvd1wFF+V1LrgeL2XBS1uRJvE91nf2PdZdZ7I6DlUC2pf6iFDuXQye/ASoX/FEEWcILUZNKCcSA2nujtFO8V9omSqCaWDe/Hx41HQq3/biczSC1x/RNCshtbYSPbNfgpBJzmKZYNcid8ICa4jRHkWFbrCtuYh5wo6wN03m1EeiDqlRmz1wvLLLQlwLtWhVwBN+BV+DTeGjR0lOdKAnzCLvrFykm3moX9tRkn404QxCqtc6+cLbmmMQ78xbIbURbQSTvAamKI+C0qwo032WR6vR9Lh3Go4LXqnCoNTuMSVxfJA+/jk6JIinre/dCZzWR+1NX9 vBhoQOvI wQPFSos+EJtdB4TUWMha5F8ah5BZuIiS15lmKlZs3Y6oyHwEqSZLjfr3js2FQ0mxo2Ztpgwqn8u5iT79pKMZV4ftMgHfLuiyxTUJqWt+AJ2/gXogRGkbX7FMRoWqrUFhU0zZJRqip5XxXVCNq9LZjy4a4KkefGRxqJcvdpWTZGIzOepp15LDSheZoDAHsRIqcknUtdlol6AlksPkGsGn5TczBALzmWoPrgSvat/Qcp4OjQprNnmDIDFSbhKsAAWN34pMkhNcv77aktbQaWj6RFH6870S7WucWvUPZQCPBUdLMkHCC1/1A0y1Pd1UMd/pmKtGi8mJijdb9hsOX75qx1/O2oQHmadzg4YEKpXT3ozRQgQke5Y9bntgDu5Qalg1TZa7V6S9GPHF0L5gPpIXzu1fZa2ViQdGFOPnq Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Hongfu Li try_ptrace() treats PTRACE_PEEKDATA return value as a boolean check. A successful read returns non-zero data (memory filled with 0x55), causing the test to incorrectly report PASS when secret memory protection is broken. Check the return value against -1 instead. The test should only pass when PTRACE_PEEKDATA fails, which means secret memory protection works. Fixes: 76fe17ef588a ("secretmem: test: add basic selftest for memfd_secret(2)") Signed-off-by: Hongfu Li Acked-by: Lorenzo Stoakes (ARM) Acked-by: Mike Rapoport (Microsoft) --- v2: - Add a comment explaining why PEEKDATA on secret memory is expected to fail, as suggested during review. - Add Acked-by from Lorenzo Stoakes and Mike Rapoport --- tools/testing/selftests/mm/memfd_secret.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/mm/memfd_secret.c b/tools/testing/selftests/mm/memfd_secret.c index c55d84c5e613..aef774be87f1 100644 --- a/tools/testing/selftests/mm/memfd_secret.c +++ b/tools/testing/selftests/mm/memfd_secret.c @@ -145,7 +145,8 @@ static void try_ptrace(int fd, int pipefd[2]) exit(KSFT_FAIL); } - if (ptrace(PTRACE_PEEKDATA, ppid, mem, 0)) + /* PEEKDATA on secret memory must fail, else protection is broken. */ + if (ptrace(PTRACE_PEEKDATA, ppid, mem, 0) == -1) exit(KSFT_PASS); exit(KSFT_FAIL); -- 2.54.0