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Message-Id: <1406053741-22795-2-git-send-email-keescook@chromium.org> Date: Tue, 22 Jul 2014 11:29:00 -0700 From: Kees Cook <keescook@...omium.org> To: linux-kernel@...r.kernel.org Cc: Kees Cook <keescook@...omium.org>, Ming Lei <ming.lei@...onical.com>, Takashi Iwai <tiwai@...e.de>, James Morris <james.l.morris@...cle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, linux-security-module@...r.kernel.org Subject: [PATCH v3 1/2] security: introduce kernel_fw_from_file hook In order to validate the contents of firmware being loaded, there must be a hook to evaluate any loaded firmware that wasn't built into the kernel itself. Without this, there is a risk that a root user could load malicious firmware designed to mount an attack against kernel memory (e.g. via DMA). Signed-off-by: Kees Cook <keescook@...omium.org> --- include/linux/security.h | 17 +++++++++++++++++ security/capability.c | 6 ++++++ security/security.c | 6 ++++++ 3 files changed, 29 insertions(+) diff --git a/include/linux/security.h b/include/linux/security.h index 9c6b9722ff48..623f90e5f38d 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -702,6 +702,15 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) * @inode points to the inode to use as a reference. * The current task must be the one that nominated @inode. * Return 0 if successful. + * @kernel_fw_from_file: + * Load firmware from userspace (not called for built-in firmware). + * @file contains the file structure pointing to the file containing + * the firmware to load. This argument will be NULL if the firmware + * was loaded via the uevent-triggered blob-based interface exposed + * by CONFIG_FW_LOADER_USER_HELPER. + * @buf pointer to buffer containing firmware contents. + * @size length of the firmware contents. + * Return 0 if permission is granted. * @kernel_module_request: * Ability to trigger the kernel to automatically upcall to userspace for * userspace to load a kernel module with the given name. @@ -1565,6 +1574,7 @@ struct security_operations { void (*cred_transfer)(struct cred *new, const struct cred *old); int (*kernel_act_as)(struct cred *new, u32 secid); int (*kernel_create_files_as)(struct cred *new, struct inode *inode); + int (*kernel_fw_from_file)(struct file *file, char *buf, size_t size); int (*kernel_module_request)(char *kmod_name); int (*kernel_module_from_file)(struct file *file); int (*task_fix_setuid) (struct cred *new, const struct cred *old, @@ -1837,6 +1847,7 @@ int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp); void security_transfer_creds(struct cred *new, const struct cred *old); int security_kernel_act_as(struct cred *new, u32 secid); int security_kernel_create_files_as(struct cred *new, struct inode *inode); +int security_kernel_fw_from_file(struct file *file, char *buf, size_t size); int security_kernel_module_request(char *kmod_name); int security_kernel_module_from_file(struct file *file); int security_task_fix_setuid(struct cred *new, const struct cred *old, @@ -2363,6 +2374,12 @@ static inline int security_kernel_create_files_as(struct cred *cred, return 0; } +static inline int security_kernel_fw_from_file(struct file *file, + char *buf, size_t size) +{ + return 0; +} + static inline int security_kernel_module_request(char *kmod_name) { return 0; diff --git a/security/capability.c b/security/capability.c index e76373de3129..a74fde6a7468 100644 --- a/security/capability.c +++ b/security/capability.c @@ -401,6 +401,11 @@ static int cap_kernel_create_files_as(struct cred *new, struct inode *inode) return 0; } +static int cap_kernel_fw_from_file(struct file *file, char *buf, size_t size) +{ + return 0; +} + static int cap_kernel_module_request(char *kmod_name) { return 0; @@ -1015,6 +1020,7 @@ void __init security_fixup_ops(struct security_operations *ops) set_to_cap_if_null(ops, cred_transfer); set_to_cap_if_null(ops, kernel_act_as); set_to_cap_if_null(ops, kernel_create_files_as); + set_to_cap_if_null(ops, kernel_fw_from_file); set_to_cap_if_null(ops, kernel_module_request); set_to_cap_if_null(ops, kernel_module_from_file); set_to_cap_if_null(ops, task_fix_setuid); diff --git a/security/security.c b/security/security.c index 31614e9e96e5..35d37d0f0d49 100644 --- a/security/security.c +++ b/security/security.c @@ -845,6 +845,12 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode) return security_ops->kernel_create_files_as(new, inode); } +int security_kernel_fw_from_file(struct file *file, char *buf, size_t size) +{ + return security_ops->kernel_fw_from_file(file, buf, size); +} +EXPORT_SYMBOL_GPL(security_kernel_fw_from_file); + int security_kernel_module_request(char *kmod_name) { return security_ops->kernel_module_request(kmod_name); -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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