Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal

Pull signal handling cleanups from Al Viro:
 "sigaltstack infrastructure + conversion for x86, alpha and um,
  COMPAT_SYSCALL_DEFINE infrastructure.

  Note that there are several conflicts between "unify
  SS_ONSTACK/SS_DISABLE definitions" and UAPI patches in mainline;
  resolution is trivial - just remove definitions of SS_ONSTACK and
  SS_DISABLED from arch/*/uapi/asm/signal.h; they are all identical and
  include/uapi/linux/signal.h contains the unified variant."

Fixed up conflicts as per Al.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal:
  alpha: switch to generic sigaltstack
  new helpers: __save_altstack/__compat_save_altstack, switch x86 and um to those
  generic compat_sys_sigaltstack()
  introduce generic sys_sigaltstack(), switch x86 and um to it
  new helper: compat_user_stack_pointer()
  new helper: restore_altstack()
  unify SS_ONSTACK/SS_DISABLE definitions
  new helper: current_user_stack_pointer()
  missing user_stack_pointer() instances
  Bury the conditionals from kernel_thread/kernel_execve series
  COMPAT_SYSCALL_DEFINE: infrastructure

3 files changed, 77 insertions, 5 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 85f6d536608d..a31b823b3c2d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1613,7 +1613,6 @@ long do_fork(unsigned long clone_flags,
         return nr;
 }
 
-#ifdef CONFIG_GENERIC_KERNEL_THREAD
 /*
  * Create a kernel thread.
  */
@@ -1622,7 +1621,6 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
         return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
                 (unsigned long)arg, NULL, NULL);
 }
-#endif
 
 #ifdef __ARCH_WANT_SYS_FORK
 SYSCALL_DEFINE0(fork)
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 1c317e386831..0023a87e8de6 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -219,9 +219,9 @@ static int ____call_usermodehelper(void *data)
 
         commit_creds(new);
 
-        retval = kernel_execve(sub_info->path,
-                               (const char *const *)sub_info->argv,
-                               (const char *const *)sub_info->envp);
+        retval = do_execve(sub_info->path,
+                           (const char __user *const __user *)sub_info->argv,
+                           (const char __user *const __user *)sub_info->envp);
         if (!retval)
                 return 0;
 
diff --git a/kernel/signal.c b/kernel/signal.c
index 580a91e63471..7aaa51d8e5b8 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -31,6 +31,7 @@
 #include <linux/nsproxy.h>
 #include <linux/user_namespace.h>
 #include <linux/uprobes.h>
+#include <linux/compat.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/signal.h>
 
@@ -3094,6 +3095,79 @@ do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long s
 out:
         return error;
 }
+#ifdef CONFIG_GENERIC_SIGALTSTACK
+SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss)
+{
+        return do_sigaltstack(uss, uoss, current_user_stack_pointer());
+}
+#endif
+
+int restore_altstack(const stack_t __user *uss)
+{
+        int err = do_sigaltstack(uss, NULL, current_user_stack_pointer());
+        /* squash all but EFAULT for now */
+        return err == -EFAULT ? err : 0;
+}
+
+int __save_altstack(stack_t __user *uss, unsigned long sp)
+{
+        struct task_struct *t = current;
+        return  __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
+                __put_user(sas_ss_flags(sp), &uss->ss_flags) |
+                __put_user(t->sas_ss_size, &uss->ss_size);
+}
+
+#ifdef CONFIG_COMPAT
+#ifdef CONFIG_GENERIC_SIGALTSTACK
+asmlinkage long compat_sys_sigaltstack(const compat_stack_t __user *uss_ptr,
+                                       compat_stack_t __user *uoss_ptr)
+{
+        stack_t uss, uoss;
+        int ret;
+        mm_segment_t seg;
+
+        if (uss_ptr) {
+                compat_stack_t uss32;
+
+                memset(&uss, 0, sizeof(stack_t));
+                if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t)))
+                        return -EFAULT;
+                uss.ss_sp = compat_ptr(uss32.ss_sp);
+                uss.ss_flags = uss32.ss_flags;
+                uss.ss_size = uss32.ss_size;
+        }
+        seg = get_fs();
+        set_fs(KERNEL_DS);
+        ret = do_sigaltstack((stack_t __force __user *) (uss_ptr ? &uss : NULL),
+                             (stack_t __force __user *) &uoss,
+                             compat_user_stack_pointer());
+        set_fs(seg);
+        if (ret >= 0 && uoss_ptr)  {
+                if (!access_ok(VERIFY_WRITE, uoss_ptr, sizeof(compat_stack_t)) ||
+                    __put_user(ptr_to_compat(uoss.ss_sp), &uoss_ptr->ss_sp) ||
+                    __put_user(uoss.ss_flags, &uoss_ptr->ss_flags) ||
+                    __put_user(uoss.ss_size, &uoss_ptr->ss_size))
+                        ret = -EFAULT;
+        }
+        return ret;
+}
+
+int compat_restore_altstack(const compat_stack_t __user *uss)
+{
+        int err = compat_sys_sigaltstack(uss, NULL);
+        /* squash all but -EFAULT for now */
+        return err == -EFAULT ? err : 0;
+}
+
+int __compat_save_altstack(compat_stack_t __user *uss, unsigned long sp)
+{
+        struct task_struct *t = current;
+        return  __put_user(ptr_to_compat((void __user *)t->sas_ss_sp), &uss->ss_sp) |
+                __put_user(sas_ss_flags(sp), &uss->ss_flags) |
+                __put_user(t->sas_ss_size, &uss->ss_size);
+}
+#endif
+#endif
 
 #ifdef __ARCH_WANT_SYS_SIGPENDING