1 files changed, 38 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 9991e2a58bf4..6f6810db0a74 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -68,6 +68,13 @@
 #define ucontext        ucontext32
 
 /*
+ * Userspace code may pass a ucontext which doesn't include VSX added
+ * at the end.  We need to check for this case.
+ */
+#define UCONTEXTSIZEWITHOUTVSX \
+                (sizeof(struct ucontext) - sizeof(elf_vsrreghalf_t32))
+
+/*
  * Returning 0 means we return to userspace via
  * ret_from_except and thus restore all user
  * registers from *regs.  This is what we need
@@ -930,12 +937,42 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
 {
         unsigned char tmp;
 
+#ifdef CONFIG_PPC64
+        unsigned long new_msr = 0;
+
+        if (new_ctx &&
+            __get_user(new_msr, &new_ctx->uc_mcontext.mc_gregs[PT_MSR]))
+                return -EFAULT;
+        /*
+         * Check that the context is not smaller than the original
+         * size (with VMX but without VSX)
+         */
+        if (ctx_size < UCONTEXTSIZEWITHOUTVSX)
+                return -EINVAL;
+        /*
+         * If the new context state sets the MSR VSX bits but
+         * it doesn't provide VSX state.
+         */
+        if ((ctx_size < sizeof(struct ucontext)) &&
+            (new_msr & MSR_VSX))
+                return -EINVAL;
+#ifdef CONFIG_VSX
+        /*
+         * If userspace doesn't provide enough room for VSX data,
+         * but current thread has used VSX, we don't have anywhere
+         * to store the full context back into.
+         */
+        if ((ctx_size < sizeof(struct ucontext)) &&
+            (current->thread.used_vsr && old_ctx))
+                return -EINVAL;
+#endif
+#else
         /* Context size is for future use. Right now, we only make sure
          * we are passed something we understand
          */
         if (ctx_size < sizeof(struct ucontext))
                 return -EINVAL;
-
+#endif
         if (old_ctx != NULL) {
                 struct mcontext __user *mctx;