[2.30 COMMITTED] Fix array overflow in backtrace on PowerPC (bug 25423)

[Patsy Griffin <patsy@redhat.com>]

From: Andreas Schwab <schwab@suse.de>

    Fix array overflow in backtrace on PowerPC (bug 25423)

    When unwinding through a signal frame the backtrace function on PowerPC
    didn't check array bounds when storing the frame address.  Fixes commit
    d400dcac5e ("PowerPC: fix backtrace to handle signal trampolines").

    (cherry picked from commit d93769405996dfc11d216ddbe415946617b5a494)

diff --git a/debug/tst-backtrace5.c b/debug/tst-backtrace5.c
index 5a5ce8bc79..aed5ee4c94 100644
--- a/debug/tst-backtrace5.c
+++ b/debug/tst-backtrace5.c
@@ -89,6 +89,18 @@ handle_signal (int signum)
       }
   /* Symbol names are not available for static functions, so we do not
      check do_test.  */
+
+  /* Check that backtrace does not return more than what fits in the array
+     (bug 25423).  */
+  for (int j = 0; j < NUM_FUNCTIONS; j++)
+    {
+      n = backtrace (addresses, j);
+      if (n > j)
+ {
+  FAIL ();
+  return;
+ }
+    }
 }

 NO_INLINE int
diff --git a/sysdeps/powerpc/powerpc32/backtrace.c
b/sysdeps/powerpc/powerpc32/backtrace.c
index 857a8aad7b..dc187a8f20 100644
--- a/sysdeps/powerpc/powerpc32/backtrace.c
+++ b/sysdeps/powerpc/powerpc32/backtrace.c
@@ -114,6 +114,8 @@ __backtrace (void **array, int size)
         }
       if (gregset)
  {
+  if (count + 1 == size)
+    break;
   array[++count] = (void*)((*gregset)[PT_NIP]);
   current = (void*)((*gregset)[PT_R1]);
  }
diff --git a/sysdeps/powerpc/powerpc64/backtrace.c
b/sysdeps/powerpc/powerpc64/backtrace.c
index 7a167838d9..ce038a139f 100644
--- a/sysdeps/powerpc/powerpc64/backtrace.c
+++ b/sysdeps/powerpc/powerpc64/backtrace.c
@@ -87,6 +87,8 @@ __backtrace (void **array, int size)
       if (is_sigtramp_address (current->return_address))
         {
   struct signal_frame_64 *sigframe = (struct signal_frame_64*) current;
+  if (count + 1 == size)
+    break;
           array[++count] = (void*)
sigframe->uc.uc_mcontext.gp_regs[PT_NIP];
   current = (void*) sigframe->uc.uc_mcontext.gp_regs[PT_R1];
  }