[nasm:nasm-2.13.xx] prepoc: Fix heap-buffer-overflow in detoken

[nasm-bot f. C. G. <gor...@gm...>]

Commit-ID:  9b7ee09abfd426b99aa1ea81d19a3b2818eeabf9
Gitweb:     http://repo.or.cz/w/nasm.git?a=commitdiff;h=9b7ee09abfd426b99aa1ea81d19a3b2818eeabf9
Author:     Cyrill Gorcunov <gor...@gm...>
AuthorDate: Sun, 22 Oct 2017 21:42:59 +0300
Committer:  Cyrill Gorcunov <gor...@gm...>
CommitDate: Sun, 22 Oct 2017 21:42:59 +0300

prepoc: Fix heap-buffer-overflow in detoken

Just make sure we've a data to process.

https://bugzilla.nasm.us/show_bug.cgi?id=3392424

Signed-off-by: Cyrill Gorcunov <gor...@gm...>


---
 asm/preproc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/asm/preproc.c b/asm/preproc.c
index 9642edc..475926d 100644
--- a/asm/preproc.c
+++ b/asm/preproc.c
@@ -1254,7 +1254,8 @@ static char *detoken(Token * tlist, bool expand_locals)
     int len = 0;
 
     list_for_each(t, tlist) {
-        if (t->type == TOK_PREPROC_ID && t->text[1] == '!') {
+        if (t->type == TOK_PREPROC_ID && t->text &&
+            t->text[0] && t->text[1] == '!') {
             char *v;
             char *q = t->text;