3 files changed, 109 insertions, 0 deletions

diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 6efd7a78de6a..79bb98d71858 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -24,6 +24,7 @@
 #include <linux/errno.h>
 #include <linux/compiler.h>
 #include <linux/workqueue.h>
+#include <linux/sysctl.h>
 
 #define KMOD_PATH_LEN 256
 
@@ -109,6 +110,8 @@ call_usermodehelper(char *path, char **argv, char **envp, enum umh_wait wait)
                                        NULL, NULL, NULL);
 }
 
+extern struct ctl_table usermodehelper_table[];
+
 extern void usermodehelper_init(void);
 
 extern int usermodehelper_disable(void);
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 9cd0591c96a2..06fdea2819b6 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);
@@ -153,6 +162,19 @@ static int ____call_usermodehelper(void *data)
                         goto fail;
         }
 
+        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);
+
+        commit_creds(new);
+
         retval = kernel_execve(sub_info->path,
                                (const char *const *)sub_info->argv,
                                (const char *const *)sub_info->envp);
@@ -418,6 +440,84 @@ 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");
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c0bb32414b17..965134bed6cd 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -56,6 +56,7 @@
 #include <linux/kprobes.h>
 #include <linux/pipe_fs_i.h>
 #include <linux/oom.h>
+#include <linux/kmod.h>
 
 #include <asm/uaccess.h>
 #include <asm/processor.h>
@@ -616,6 +617,11 @@ static struct ctl_table kern_table[] = {
                 .child          = random_table,
         },
         {
+                .procname       = "usermodehelper",
+                .mode           = 0555,
+                .child          = usermodehelper_table,
+        },
+        {
                 .procname       = "overflowuid",
                 .data           = &overflowuid,
                 .maxlen         = sizeof(int),