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Tue, 28 Jul 2026 20:37:09 -0700 (PDT) From: Coiby Xu To: kexec@lists.infradead.org Cc: Andrew Morton , Sourabh Jain , Baoquan He , Dave Young , Pratyush Yadav , Mike Rapoport , Pasha Tatashin , Coiby Xu , linux-kernel@vger.kernel.org (open list) Subject: [PATCH v3 03/10] crash_dump: Disallow writing to dm-crypt configfs during kexec_file_load syscall Date: Wed, 29 Jul 2026 11:36:43 +0800 Message-ID: <20260729033654.311541-4-coiby.xu@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260729033654.311541-1-coiby.xu@gmail.com> References: <20260729033654.311541-1-coiby.xu@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. 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 | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c index 4335b6cb1fc4..d2e66c6fe6f3 100644 --- a/kernel/crash_dump_dm_crypt.c +++ b/kernel/crash_dump_dm_crypt.c @@ -293,6 +293,7 @@ static ssize_t config_keys_reuse_show(struct config_item *item, char *page) static ssize_t config_keys_reuse_store(struct config_item *item, const char *page, size_t count) { + struct mutex *lock; bool val; int r; @@ -302,8 +303,12 @@ static ssize_t config_keys_reuse_store(struct config_item *item, return -EINVAL; } + lock = &to_config_group(item)->cg_subsys->su_mutex; + mutex_lock(lock); + + r = -EINVAL; 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"); @@ -311,11 +316,15 @@ 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; } + r = count; + +unlock: + mutex_unlock(lock); return count; } @@ -421,6 +430,8 @@ static int build_keys_header(void) return 0; } +static bool mutex_acquired; + int crash_load_dm_crypt_keys(struct kimage *image) { struct kexec_buf kbuf = { @@ -432,6 +443,9 @@ int crash_load_dm_crypt_keys(struct kimage *image) }; int r = 0; + mutex_lock(&config_keys_subsys.su_mutex); + mutex_acquired = true; + if (key_count <= 0) { kexec_dprintk("No dm-crypt keys\n"); return 0; @@ -481,6 +495,11 @@ void kexec_file_post_load_cleanup_dm_crypt(struct kimage *image) kfree_sensitive(keys_header); keys_header = NULL; } + + if (mutex_acquired) { + mutex_unlock(&config_keys_subsys.su_mutex); + mutex_acquired = false; + } } static int __init configfs_dmcrypt_keys_init(void) -- 2.55.0