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security: introduce kernel_fw_from_file hook

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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@chromium.org>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Kees Cook 2014-02-25 10:28:04 -08:00
parent 7d8b6c6375
commit 13752fe2d7
3 changed files with 29 additions and 0 deletions
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17
include/linux/security.h
View File

@ -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.
@ -1568,6 +1577,7 @@ 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,
@ -1840,6 +1850,7 @@ 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,
@ -2366,6 +2377,12 @@ 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;

6
security/capability.c
View File

@ -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);

6
security/security.c
View File

@ -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);