[aarch64] Allocate enough space for err_str in aarch64_handle_attr_branch_protection

[Matthew Malcomson]

-fsanitize=hwaddress found a one-byte overwrite when running the
testsuite here.  aarch64_handle_attr_branch_protection allocates
`strlen(str)` bytes for an error string, which is populated by
`strcpy(..., str)` in the case where the branch protection string is
completely invalid.

Tested on aarch64 with hwasan (though not a full bootstrap since it's
obvious).

gcc/ChangeLog:

2019-11-05  Matthew Malcomson  <matthew.malcom...@arm.com>

        * config/aarch64/aarch64.c (aarch64_handle_attr_cpu): Allocate
        enough bytes for the NULL character.



###############     Attachment also inlined for ease of reply    ###############


diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 
232317d4a5a4a16529f573eef5a8d7a068068207..fc03faa8f8d459a84024d4394fff375b72d31264
 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -13298,7 +13298,7 @@ aarch64_handle_attr_cpu (const char *str)
  static bool
  aarch64_handle_attr_branch_protection (const char* str)
  {
-  char *err_str = (char *) xmalloc (strlen (str));
+  char *err_str = (char *) xmalloc (strlen (str) + 1);
   enum aarch64_parse_opt_result res = aarch64_parse_branch_protection (str,
                                                                      &err_str);
   bool success = false;


diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 
232317d4a5a4a16529f573eef5a8d7a068068207..fc03faa8f8d459a84024d4394fff375b72d31264
 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -13298,7 +13298,7 @@ aarch64_handle_attr_cpu (const char *str)
  static bool
  aarch64_handle_attr_branch_protection (const char* str)
  {
-  char *err_str = (char *) xmalloc (strlen (str));
+  char *err_str = (char *) xmalloc (strlen (str) + 1);
   enum aarch64_parse_opt_result res = aarch64_parse_branch_protection (str,
                                                                      &err_str);
   bool success = false;