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[2a03:2880:30ff:8::face:b00c]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aa4f436c412sm60692166b.179.2024.11.21.01.57.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Nov 2024 01:57:28 -0800 (PST) From: Breno Leitao Date: Thu, 21 Nov 2024 01:57:12 -0800 Subject: [PATCH v2] ima: kexec: silence RCU list traversal warning Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20241121-ima_rcu-v2-1-4d48630cf2c6@debian.org> X-B4-Tracking: v=1; b=H4sIAPcDP2cC/2XMMQ7CIBQA0KuQPxcDCFKZvIdpDMK3/YNgQImm4 e7Grq5veCtULIQVHFuhYKNKOYFjamAQFp9m5BTBMVBCaSmF5nT3lxJeHHHcRz/aKIyAgcGj4I3 e23SeBgYL1Wcuny1u8qf/R5NcciON1QcRzFHYU8Qr+bTLZYap9/4FUVfrFp8AAAA= X-Change-ID: 20241104-ima_rcu-ee83da87d050 To: Mimi Zohar , Roberto Sassu , Dmitry Kasatkin , Eric Snowberg , Paul Moore , James Morris , "Serge E. Hallyn" , "Eric W. Biederman" , Andrew Morton Cc: Mimi Zohar , linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Breno Leitao X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=1865; i=leitao@debian.org; h=from:subject:message-id; bh=mXE/tvgFt0bXqhIgNFNLrntXXGNOV3Lq+zjQqIpTj3s=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBnPwQHUPDLWuedaB6ehCHozdKpH5lLrUX4VJvc1 /GUz1Fu5AGJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCZz8EBwAKCRA1o5Of/Hh3 bfoWD/9V3QR+gu4NonzlOTUolGXozhUyVj7t/ynvxnIY6gQw/KFarveBDzIE1Gf8QDp9T4BOn6a BqXlKNssfsh7V4K+L8O7P09b4OfdjF6g2drULQ9qYB3V9Rz/7vLr2j9/FLcKl/C7IVJjYXGVuVU TQNIGc9+QDuEqbMZZPqCdnjmYliKGOKoHoDTfJSohLHxukbDrrd4vIVYPMfSVbwDbZyxvJ83LzS hEs4koOdH/3Uw2HNLg0R/v1VR74kiox/8HnBB9c6+bXjNmHOXBzBsMFBBu54Ke6Pa4iKbaKwJKA LhgLzP45Q6/QOiQWQE0E7C0PSTNtRdrDckrUG+ICzrYdIzCCPa9ya4q3KI8QOCMIHWsXjp7UC+F XaCJXzI7LJyfRmFHcCWcpQwXMHwpZrajVK9SPeXGNFCBg1oqp96ZDLxxxrIsoOLf7R45BfWXxwC 1Gsw05C2ojyzjnyTq/0pjxv4bj6d0E5Z5ETaAhFtSbyCx8m5yZDeQScSf3bF9uT//qaQAzhGBM/ d9zEDWZJKl24s+PPNLSFBm2zCOycfEMMWYtxSwxlxJtnRMEYhGJVjqFQdevxHxxfkuhuDjyvUlN ZFtbyZeLUB/WtuewnrW4V1MkYfQk76pAixhTvmRamBlfe5EZ1WCuVGIdAYbrSnoncRpL/EmbX9a 8Wq/wQAs4j41rgg== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D The ima_measurements list is append-only and doesn't require rcu_read_lock() protection. However, lockdep issues a warning when traversing RCU lists without the read lock: security/integrity/ima/ima_kexec.c:40 RCU-list traversed in non-reader section!! Fix this by using the variant of list_for_each_entry_rcu() with the last argument set to true. This tells the RCU subsystem that traversing this append-only list without the read lock is intentional and safe. This change silences the lockdep warning while maintaining the correct semantics for the append-only list traversal. Signed-off-by: Breno Leitao --- Changes in v2: - Do not hold the RCU read lock, but, annotate list_for_each_entry_rcu() that is OK to traverse the list without the RCU read lock. - Link to v1: https://lore.kernel.org/r/20241104-ima_rcu-v1-1-5157460c5907@debian.org --- security/integrity/ima/ima_kexec.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- base-commit: ac24e26aa08fe026804f678599f805eb13374a5d change-id: 20241104-ima_rcu-ee83da87d050 Best regards, diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c index 52e00332defed39774c9e23e045f1377cfa30d0c..9d45f4d26f731658a79b94b9f95f4dcc4dcb6325 100644 --- a/security/integrity/ima/ima_kexec.c +++ b/security/integrity/ima/ima_kexec.c @@ -37,7 +37,8 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer, memset(&khdr, 0, sizeof(khdr)); khdr.version = 1; - list_for_each_entry_rcu(qe, &ima_measurements, later) { + /* This is an append-only list, no need to hold the RCU read lock */ + list_for_each_entry_rcu(qe, &ima_measurements, later, true) { if (file.count < file.size) { khdr.count++; ima_measurements_show(&file, qe);