commit 30d251c35871b0e8aff16d60df3db3d327e34bfa
Author: Sandra Loosemore <sandra@codesourcery.com>
Date:   Wed Apr 24 08:53:26 2019 -0700

    Fix CVE-2017-9778.
    
    GDB was failing to catch cases where a corrupt ELF or core file
    contained an invalid length value in a Dwarf debug frame FDE header.
    It was checking for buffer overflow but not cases where the length was
    negative or caused pointer wrap-around.
    
    In addition to the additional validity check, this patch cleans up the
    multiple signed/unsigned conversions on the length field so that an
    unsigned representation is used consistently throughout.
    
    2019-04-24  Sandra Loosemore  <sandra@codesourcery.com>
    	    Kang Li <kanglictf@gmail.com>
    
    	PR gdb/21600
    
    	* dwarf2-frame.c (read_initial_length): Be consistent about using
    	unsigned representation of length.
    	(decode_frame_entry_1): Likewise.  Check for wraparound of
    	end pointer as well as buffer overflow.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 5c40683..deab585 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,13 @@
+2019-04-24  Sandra Loosemore  <sandra@codesourcery.com>
+	    Kang Li <kanglictf@gmail.com>
+
+	PR gdb/21600
+
+	* dwarf2-frame.c (read_initial_length): Be consistent about using
+	unsigned representation of length.
+	(decode_frame_entry_1): Likewise.  Check for wraparound of
+	end pointer as well as buffer overflow.
+
 2019-04-23  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* s12z-tdep.c (s12z_unwind_pc): Delete.
diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
index e2bf61b..b697afa 100644
--- a/gdb/dwarf2-frame.c
+++ b/gdb/dwarf2-frame.c
@@ -1487,7 +1487,7 @@ static ULONGEST
 read_initial_length (bfd *abfd, const gdb_byte *buf,
 		     unsigned int *bytes_read_ptr)
 {
-  LONGEST result;
+  ULONGEST result;
 
   result = bfd_get_32 (abfd, buf);
   if (result == 0xffffffff)
@@ -1788,7 +1788,7 @@ decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start,
 {
   struct gdbarch *gdbarch = get_objfile_arch (unit->objfile);
   const gdb_byte *buf, *end;
-  LONGEST length;
+  ULONGEST length;
   unsigned int bytes_read;
   int dwarf64_p;
   ULONGEST cie_id;
@@ -1799,15 +1799,15 @@ decode_frame_entry_1 (struct comp_unit *unit, const gdb_byte *start,
   buf = start;
   length = read_initial_length (unit->abfd, buf, &bytes_read);
   buf += bytes_read;
-  end = buf + length;
-
-  /* Are we still within the section?  */
-  if (end > unit->dwarf_frame_buffer + unit->dwarf_frame_size)
-    return NULL;
+  end = buf + (size_t) length;
 
   if (length == 0)
     return end;
 
+  /* Are we still within the section?  */
+  if (end <= buf || end > unit->dwarf_frame_buffer + unit->dwarf_frame_size)
+    return NULL;
+
   /* Distinguish between 32 and 64-bit encoded frame info.  */
   dwarf64_p = (bytes_read == 12);