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

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

[Tulio Magno Quites Machado Filho]

From: Andreas Schwab <schwab@suse.de>

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)
---
 NEWS                                  |  1 +
 debug/tst-backtrace5.c                | 12 ++++++++++++
 sysdeps/powerpc/powerpc32/backtrace.c |  2 ++
 sysdeps/powerpc/powerpc64/backtrace.c |  2 ++
 4 files changed, 17 insertions(+)

diff --git a/NEWS b/NEWS
index 3ccaae3968..cb62587dbb 100644
--- a/NEWS
+++ b/NEWS
@@ -190,6 +190,7 @@ The following bugs are resolved with this release:
   [24155] x32 memcmp can treat positive length as 0 (if sign bit in RDX is set) (CVE-2019-7309)
   [25203] libio: Disable vtable validation for pre-2.1 interposed handles
   [25204] Ignore LD_PREFER_MAP_32BIT_EXEC for SUID programs
+  [25423] Array overflow in backtrace on powerpc
 
 \f
 Version 2.26
diff --git a/debug/tst-backtrace5.c b/debug/tst-backtrace5.c
index 0b85e4482e..57b7dee0f6 100644
--- a/debug/tst-backtrace5.c
+++ b/debug/tst-backtrace5.c
@@ -88,6 +88,18 @@ 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 187c3b3349..f0a67008d9 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 919bf1cfd7..dd25b90bfc 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];
 	}
-- 
2.24.1