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Tue, 08 Sep 2026 17:37:13 -0700 (PDT) Received: from localhost ([2400:ac40:62f:1b67:ddd8:990d:9d6f:13b8]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39b083e4fafsm34284184a91.1.2026.09.08.17.37.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Sep 2026 17:37:12 -0700 (PDT) From: Coiby Xu To: kexec@lists.infradead.org Cc: Andrew Morton , Sourabh Jain , Baoquan He , Dave Young , Pratyush Yadav , Will Deacon , linux-arm-kernel@lists.infradead.org, Jinjie Ruan , Mike Rapoport , Pasha Tatashin , linux-kernel@vger.kernel.org (open list) Subject: [PATCH v5 3/9] crash_dump: Disallow writing to dm-crypt configfs during kexec_file_load syscall Date: Wed, 9 Sep 2026 08:36:45 +0800 Message-ID: <20260909003657.1570544-4-coiby.xu@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260909003657.1570544-1-coiby.xu@gmail.com> References: <20260909003657.1570544-1-coiby.xu@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260908_173714_232150_49131344 X-CRM114-Status: GOOD ( 16.04 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org If writing to the configfs group happens concurrently during kexec_file_load syscall, it may lead to the following issues, - buffer overflow if dm-crypt keys are added after allocation - stale total_keys if dm-crypt keys are removed during iteration - keys_header will not be freed if config/crash_dm_crypt_key/reuse is set true So hold config_keys_subsys.su_mutex for the entire sequence during the kexec_file_load syscall to ensure a consistent snapshot. To have serial access to config/crash_dm_crypt_key/reuse, use the kexec lock as we also need to access kexec_crash_image serially. Fixes: 479e58549b0f ("crash_dump: store dm crypt keys in kdump reserved memory") Suggested-by: Sourabh Jain Signed-off-by: Coiby Xu --- kernel/crash_dump_dm_crypt.c | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c index 3a416933979f..580534d43b66 100644 --- a/kernel/crash_dump_dm_crypt.c +++ b/kernel/crash_dump_dm_crypt.c @@ -7,6 +7,7 @@ #include #include #include +#include "kexec_internal.h" #define KEY_NUM_MAX 128 /* maximum dm crypt keys */ #define KEY_SIZE_MAX 256 /* maximum dm crypt key size */ @@ -306,14 +307,20 @@ static ssize_t config_keys_reuse_store(struct config_item *item, bool val; int r; + if (!kexec_trylock()) { + pr_warn("Failed to acquire the kexec lock\n"); + return -EBUSY; + } + + r = -EINVAL; if (!kexec_crash_image || !kexec_crash_image->dm_crypt_keys_addr) { kexec_dprintk( "dm-crypt keys haven't be saved to crash-reserved memory\n"); - return -EINVAL; + goto unlock; } if (kstrtobool(page, &val) || !val) - return -EINVAL; + goto unlock; if (is_dm_key_reused) { pr_info("Already got dm-crypt keys, please continue with kexec_file_load syscall\n"); @@ -321,12 +328,15 @@ static ssize_t config_keys_reuse_store(struct config_item *item, r = get_keys_from_kdump_reserved_memory(); if (r) { pr_warn("Failed to get dm-crypt keys from reserved memory\n"); - return r; + goto unlock; } is_dm_key_reused = true; } - return count; + r = count; +unlock: + kexec_unlock(); + return r; } CONFIGFS_ATTR(config_keys_, reuse); @@ -443,15 +453,17 @@ int crash_load_dm_crypt_keys(struct kimage *image) int r = 0; if (!is_dm_key_reused) { + mutex_lock(&config_keys_subsys.su_mutex); + if (key_count <= 0) { kexec_dprintk("No dm-crypt keys\n"); r = 0; - goto out; + goto unlock; } r = build_keys_header(); if (r) - goto out; + goto unlock; } /* @@ -478,6 +490,9 @@ int crash_load_dm_crypt_keys(struct kimage *image) "Loaded dm crypt keys to kexec_buffer bufsz=0x%lx memsz=0x%lx\n", kbuf.bufsz, kbuf.memsz); +unlock: + mutex_unlock(&config_keys_subsys.su_mutex); + out: is_dm_key_reused = false; return r; -- 2.55.0