1 files changed, 94 insertions, 38 deletions

diff --git a/kernel/capability.c b/kernel/capability.c
index 39e8193b41ea..901e0fdc3fff 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -53,11 +53,95 @@ static void warn_legacy_capability_use(void)
 }
 
 /*
+ * Version 2 capabilities worked fine, but the linux/capability.h file
+ * that accompanied their introduction encouraged their use without
+ * the necessary user-space source code changes. As such, we have
+ * created a version 3 with equivalent functionality to version 2, but
+ * with a header change to protect legacy source code from using
+ * version 2 when it wanted to use version 1. If your system has code
+ * that trips the following warning, it is using version 2 specific
+ * capabilities and may be doing so insecurely.
+ *
+ * The remedy is to either upgrade your version of libcap (to 2.10+,
+ * if the application is linked against it), or recompile your
+ * application with modern kernel headers and this warning will go
+ * away.
+ */
+
+static void warn_deprecated_v2(void)
+{
+        static int warned;
+
+        if (!warned) {
+                char name[sizeof(current->comm)];
+
+                printk(KERN_INFO "warning: `%s' uses deprecated v2"
+                       " capabilities in a way that may be insecure.\n",
+                       get_task_comm(name, current));
+                warned = 1;
+        }
+}
+
+/*
+ * Version check. Return the number of u32s in each capability flag
+ * array, or a negative value on error.
+ */
+static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
+{
+        __u32 version;
+
+        if (get_user(version, &header->version))
+                return -EFAULT;
+
+        switch (version) {
+        case _LINUX_CAPABILITY_VERSION_1:
+                warn_legacy_capability_use();
+                *tocopy = _LINUX_CAPABILITY_U32S_1;
+                break;
+        case _LINUX_CAPABILITY_VERSION_2:
+                warn_deprecated_v2();
+                /*
+                 * fall through - v3 is otherwise equivalent to v2.
+                 */
+        case _LINUX_CAPABILITY_VERSION_3:
+                *tocopy = _LINUX_CAPABILITY_U32S_3;
+                break;
+        default:
+                if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
+                        return -EFAULT;
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+/*
  * For sys_getproccap() and sys_setproccap(), any of the three
  * capability set pointers may be NULL -- indicating that that set is
  * uninteresting and/or not to be changed.
  */
 
+/*
+ * Atomically modify the effective capabilities returning the original
+ * value. No permission check is performed here - it is assumed that the
+ * caller is permitted to set the desired effective capabilities.
+ */
+kernel_cap_t cap_set_effective(const kernel_cap_t pE_new)
+{
+        kernel_cap_t pE_old;
+
+        spin_lock(&task_capability_lock);
+
+        pE_old = current->cap_effective;
+        current->cap_effective = pE_new;
+
+        spin_unlock(&task_capability_lock);
+
+        return pE_old;
+}
+
+EXPORT_SYMBOL(cap_set_effective);
+
 /**
  * sys_capget - get the capabilities of a given process.
  * @header: pointer to struct that contains capability version and
@@ -71,27 +155,13 @@ asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
 {
         int ret = 0;
         pid_t pid;
-        __u32 version;
         struct task_struct *target;
         unsigned tocopy;
         kernel_cap_t pE, pI, pP;
 
-        if (get_user(version, &header->version))
-                return -EFAULT;
-
-        switch (version) {
-        case _LINUX_CAPABILITY_VERSION_1:
-                warn_legacy_capability_use();
-                tocopy = _LINUX_CAPABILITY_U32S_1;
-                break;
-        case _LINUX_CAPABILITY_VERSION_2:
-                tocopy = _LINUX_CAPABILITY_U32S_2;
-                break;
-        default:
-                if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
-                        return -EFAULT;
-                return -EINVAL;
-        }
+        ret = cap_validate_magic(header, &tocopy);
+        if (ret != 0)
+                return ret;
 
         if (get_user(pid, &header->pid))
                 return -EFAULT;
@@ -118,7 +188,7 @@ out:
         spin_unlock(&task_capability_lock);
 
         if (!ret) {
-                struct __user_cap_data_struct kdata[_LINUX_CAPABILITY_U32S];
+                struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
                 unsigned i;
 
                 for (i = 0; i < tocopy; i++) {
@@ -128,7 +198,7 @@ out:
                 }
 
                 /*
-                 * Note, in the case, tocopy < _LINUX_CAPABILITY_U32S,
+                 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
                  * we silently drop the upper capabilities here. This
                  * has the effect of making older libcap
                  * implementations implicitly drop upper capability
@@ -240,30 +310,16 @@ static inline int cap_set_all(kernel_cap_t *effective,
  */
 asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
 {
-        struct __user_cap_data_struct kdata[_LINUX_CAPABILITY_U32S];
+        struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
         unsigned i, tocopy;
         kernel_cap_t inheritable, permitted, effective;
-        __u32 version;
         struct task_struct *target;
         int ret;
         pid_t pid;
 
-        if (get_user(version, &header->version))
-                return -EFAULT;
-
-        switch (version) {
-        case _LINUX_CAPABILITY_VERSION_1:
-                warn_legacy_capability_use();
-                tocopy = _LINUX_CAPABILITY_U32S_1;
-                break;
-        case _LINUX_CAPABILITY_VERSION_2:
-                tocopy = _LINUX_CAPABILITY_U32S_2;
-                break;
-        default:
-                if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
-                        return -EFAULT;
-                return -EINVAL;
-        }
+        ret = cap_validate_magic(header, &tocopy);
+        if (ret != 0)
+                return ret;
 
         if (get_user(pid, &header->pid))
                 return -EFAULT;
@@ -281,7 +337,7 @@ asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
                 permitted.cap[i] = kdata[i].permitted;
                 inheritable.cap[i] = kdata[i].inheritable;
         }
-        while (i < _LINUX_CAPABILITY_U32S) {
+        while (i < _KERNEL_CAPABILITY_U32S) {
                 effective.cap[i] = 0;
                 permitted.cap[i] = 0;
                 inheritable.cap[i] = 0;