1 files changed, 114 insertions, 10 deletions

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 9cd0591c96a2..47613dfb7b28 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -25,6 +25,7 @@
 #include <linux/kmod.h>
 #include <linux/slab.h>
 #include <linux/completion.h>
+#include <linux/cred.h>
 #include <linux/file.h>
 #include <linux/fdtable.h>
 #include <linux/workqueue.h>
@@ -43,6 +44,13 @@ extern int max_threads;
 
 static struct workqueue_struct *khelper_wq;
 
+#define CAP_BSET        (void *)1
+#define CAP_PI          (void *)2
+
+static kernel_cap_t usermodehelper_bset = CAP_FULL_SET;
+static kernel_cap_t usermodehelper_inheritable = CAP_FULL_SET;
+static DEFINE_SPINLOCK(umh_sysctl_lock);
+
 #ifdef CONFIG_MODULES
 
 /*
@@ -132,6 +140,7 @@ EXPORT_SYMBOL(__request_module);
 static int ____call_usermodehelper(void *data)
 {
         struct subprocess_info *sub_info = data;
+        struct cred *new;
         int retval;
 
         spin_lock_irq(&current->sighand->siglock);
@@ -147,12 +156,27 @@ static int ____call_usermodehelper(void *data)
          */
         set_user_nice(current, 0);
 
+        retval = -ENOMEM;
+        new = prepare_kernel_cred(current);
+        if (!new)
+                goto fail;
+
+        spin_lock(&umh_sysctl_lock);
+        new->cap_bset = cap_intersect(usermodehelper_bset, new->cap_bset);
+        new->cap_inheritable = cap_intersect(usermodehelper_inheritable,
+                                             new->cap_inheritable);
+        spin_unlock(&umh_sysctl_lock);
+
         if (sub_info->init) {
-                retval = sub_info->init(sub_info);
-                if (retval)
+                retval = sub_info->init(sub_info, new);
+                if (retval) {
+                        abort_creds(new);
                         goto fail;
+                }
         }
 
+        commit_creds(new);
+
         retval = kernel_execve(sub_info->path,
                                (const char *const *)sub_info->argv,
                                (const char *const *)sub_info->envp);
@@ -245,7 +269,6 @@ static void __call_usermodehelper(struct work_struct *work)
         }
 }
 
-#ifdef CONFIG_PM_SLEEP
 /*
  * If set, call_usermodehelper_exec() will exit immediately returning -EBUSY
  * (used for preventing user land processes from being created after the user
@@ -301,6 +324,15 @@ void usermodehelper_enable(void)
         usermodehelper_disabled = 0;
 }
 
+/**
+ * usermodehelper_is_disabled - check if new helpers are allowed to be started
+ */
+bool usermodehelper_is_disabled(void)
+{
+        return usermodehelper_disabled;
+}
+EXPORT_SYMBOL_GPL(usermodehelper_is_disabled);
+
 static void helper_lock(void)
 {
         atomic_inc(&running_helpers);
@@ -312,12 +344,6 @@ static void helper_unlock(void)
         if (atomic_dec_and_test(&running_helpers))
                 wake_up(&running_helpers_waitq);
 }
-#else /* CONFIG_PM_SLEEP */
-#define usermodehelper_disabled 0
-
-static inline void helper_lock(void) {}
-static inline void helper_unlock(void) {}
-#endif /* CONFIG_PM_SLEEP */
 
 /**
  * call_usermodehelper_setup - prepare to call a usermode helper
@@ -364,7 +390,7 @@ EXPORT_SYMBOL(call_usermodehelper_setup);
  * context in which call_usermodehelper_exec is called.
  */
 void call_usermodehelper_setfns(struct subprocess_info *info,
-                    int (*init)(struct subprocess_info *info),
+                    int (*init)(struct subprocess_info *info, struct cred *new),
                     void (*cleanup)(struct subprocess_info *info),
                     void *data)
 {
@@ -418,6 +444,84 @@ unlock:
 }
 EXPORT_SYMBOL(call_usermodehelper_exec);
 
+static int proc_cap_handler(struct ctl_table *table, int write,
+                         void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        struct ctl_table t;
+        unsigned long cap_array[_KERNEL_CAPABILITY_U32S];
+        kernel_cap_t new_cap;
+        int err, i;
+
+        if (write && (!capable(CAP_SETPCAP) ||
+                      !capable(CAP_SYS_MODULE)))
+                return -EPERM;
+
+        /*
+         * convert from the global kernel_cap_t to the ulong array to print to
+         * userspace if this is a read.
+         */
+        spin_lock(&umh_sysctl_lock);
+        for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)  {
+                if (table->data == CAP_BSET)
+                        cap_array[i] = usermodehelper_bset.cap[i];
+                else if (table->data == CAP_PI)
+                        cap_array[i] = usermodehelper_inheritable.cap[i];
+                else
+                        BUG();
+        }
+        spin_unlock(&umh_sysctl_lock);
+
+        t = *table;
+        t.data = &cap_array;
+
+        /*
+         * actually read or write and array of ulongs from userspace.  Remember
+         * these are least significant 32 bits first
+         */
+        err = proc_doulongvec_minmax(&t, write, buffer, lenp, ppos);
+        if (err < 0)
+                return err;
+
+        /*
+         * convert from the sysctl array of ulongs to the kernel_cap_t
+         * internal representation
+         */
+        for (i = 0; i < _KERNEL_CAPABILITY_U32S; i++)
+                new_cap.cap[i] = cap_array[i];
+
+        /*
+         * Drop everything not in the new_cap (but don't add things)
+         */
+        spin_lock(&umh_sysctl_lock);
+        if (write) {
+                if (table->data == CAP_BSET)
+                        usermodehelper_bset = cap_intersect(usermodehelper_bset, new_cap);
+                if (table->data == CAP_PI)
+                        usermodehelper_inheritable = cap_intersect(usermodehelper_inheritable, new_cap);
+        }
+        spin_unlock(&umh_sysctl_lock);
+
+        return 0;
+}
+
+struct ctl_table usermodehelper_table[] = {
+        {
+                .procname       = "bset",
+                .data           = CAP_BSET,
+                .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
+                .mode           = 0600,
+                .proc_handler   = proc_cap_handler,
+        },
+        {
+                .procname       = "inheritable",
+                .data           = CAP_PI,
+                .maxlen         = _KERNEL_CAPABILITY_U32S * sizeof(unsigned long),
+                .mode           = 0600,
+                .proc_handler   = proc_cap_handler,
+        },
+        { }
+};
+
 void __init usermodehelper_init(void)
 {
         khelper_wq = create_singlethread_workqueue("khelper");