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: Eric Paris <eparis@xxxxxxxxxx>
---
include/linux/security.h | 10 ++++++++++
kernel/kmod.c | 4 ++++
security/capability.c | 6 ++++++
security/security.c | 5 +++++
4 files changed, 25 insertions(+), 0 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index d5f6578..34c5465 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -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
@@ -1500,6 +1503,7 @@ 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);
@@ -1755,6 +1759,7 @@ 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);
@@ -2306,6 +2311,11 @@ 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)
{
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 385c31a..5a7ae57 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -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);
diff --git a/security/capability.c b/security/capability.c
index 4f23f4f..06400cf 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -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;
@@ -961,6 +966,7 @@ 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);
diff --git a/security/security.c b/security/security.c
index b98c684..f88eaf6 100644
--- a/security/security.c
+++ b/security/security.c
@@ -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);
--
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