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Commit 9188499c authored by Eric Paris's avatar Eric Paris Committed by James Morris
Browse files

security: introducing security_request_module 



Calling request_module() will trigger a userspace upcall which will load a
new module into the kernel.  This can be a dangerous event if the process
able to trigger request_module() is able to control either the modprobe
binary or the module binary.  This patch adds a new security hook to
request_module() which can be used by an LSM to control a processes ability
to call request_module().

Signed-off-by: default avatarEric Paris <eparis@redhat.com>
Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent a8f80e8f

include/linux/security.h

+10 −0
Original line number Diff line number Diff line
@@ -678,6 +678,9 @@ 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_module_request:

 *	Ability to trigger the kernel to automatically upcall to userspace for

 *	userspace to load a kernel module with the given name.

 * @task_setuid:

 *	Check permission before setting one or more of the user identity

 *	attributes of the current process.  The @flags parameter indicates
@@ -1489,6 +1492,7 @@ struct security_operations { 
	void (*cred_commit)(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_module_request)(void);

	int (*task_setuid) (uid_t id0, uid_t id1, uid_t id2, int flags);

	int (*task_fix_setuid) (struct cred *new, const struct cred *old,

				int flags);
@@ -1741,6 +1745,7 @@ int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp); 
void security_commit_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_module_request(void);

int security_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags);

int security_task_fix_setuid(struct cred *new, const struct cred *old,

			     int flags);
@@ -2292,6 +2297,11 @@ static inline int security_kernel_create_files_as(struct cred *cred, 
	return 0;

}



static inline int security_kernel_module_request(void)

{

	return 0;

}



static inline int security_task_setuid(uid_t id0, uid_t id1, uid_t id2,

				       int flags)

{

kernel/kmod.c

+4 −0
Original line number Diff line number Diff line
@@ -78,6 +78,10 @@ int __request_module(bool wait, const char *fmt, ...) 
#define MAX_KMOD_CONCURRENT 50	/* Completely arbitrary value - KAO */

	static int kmod_loop_msg;



	ret = security_kernel_module_request();

	if (ret)

		return ret;



	va_start(args, fmt);

	ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);

	va_end(args);

security/capability.c

+6 −0
Original line number Diff line number Diff line
@@ -396,6 +396,11 @@ static int cap_kernel_create_files_as(struct cred *new, struct inode *inode) 
	return 0;

}



static int cap_kernel_module_request(void)

{

	return 0;

}



static int cap_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags)

{

	return 0;
@@ -945,6 +950,7 @@ void security_fixup_ops(struct security_operations *ops) 
	set_to_cap_if_null(ops, cred_commit);

	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_module_request);

	set_to_cap_if_null(ops, task_setuid);

	set_to_cap_if_null(ops, task_fix_setuid);

	set_to_cap_if_null(ops, task_setgid);

security/security.c

+5 −0
Original line number Diff line number Diff line
@@ -709,6 +709,11 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode) 
	return security_ops->kernel_create_files_as(new, inode);

}



int security_kernel_module_request(void)

{

	return security_ops->kernel_module_request();

}



int security_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags)

{

	return security_ops->task_setuid(id0, id1, id2, flags);