1 files changed, 32 insertions, 4 deletions

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 93ebfb6944b6..5f9d2ef2e24b 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -268,6 +268,13 @@ static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
 }
 
 /*
+ * 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) - 32*sizeof(long))
+
+/*
  * Handle {get,set,swap}_context operations
  */
 int sys_swapcontext(struct ucontext __user *old_ctx,
@@ -276,13 +283,34 @@ int sys_swapcontext(struct ucontext __user *old_ctx,
 {
         unsigned char tmp;
         sigset_t set;
+        unsigned long new_msr = 0;
 
-        /* Context size is for future use. Right now, we only make sure
-         * we are passed something we understand
+        if (new_ctx &&
+            __get_user(new_msr, &new_ctx->uc_mcontext.gp_regs[PT_MSR]))
+                return -EFAULT;
+        /*
+         * Check that the context is not smaller than the original
+         * size (with VMX but without VSX)
          */
-        if (ctx_size < sizeof(struct ucontext))
+        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
         if (old_ctx != NULL) {
                 if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
                     || setup_sigcontext(&old_ctx->uc_mcontext, regs, 0, NULL, 0)