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

[Andreas Schwab]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d93769405996dfc11d216ddbe415946617b5a494

commit d93769405996dfc11d216ddbe415946617b5a494
Author: Andreas Schwab <schwab@suse.de>
Date:   Mon Jan 20 17:01:50 2020 +0100

    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").

Diff:
---
 debug/tst-backtrace5.c                | 12 ++++++++++++
 sysdeps/powerpc/powerpc32/backtrace.c |  2 ++
 sysdeps/powerpc/powerpc64/backtrace.c |  2 ++
 3 files changed, 16 insertions(+)

diff --git a/debug/tst-backtrace5.c b/debug/tst-backtrace5.c
index e7ce410..b2f4616 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 7c2d472..d1456c8 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 65c260a..8a53a10 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];
 	}