[PATCH nft] parser: fix crash if we add a chain with an error chain type

[Liping Zhang]

From: Liping Zhang <liping.zh...@spreadtrum.com>

If we add a chain and specify the nonexistent chain type, chain_type_name_lookup
will return a NULL pointer, and meet the assert condition in xstrdup.
Fix crash like this:

  # nft add chain filter input {type none hook input priority 0\;}
  nft: utils.c:63: xstrdup: Assertion `s != ((void *)0)' failed.
  Aborted (core dumped)

Signed-off-by: Liping Zhang <liping.zh...@spreadtrum.com>
---
 src/parser_bison.y | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/parser_bison.y b/src/parser_bison.y
index 0452b8f..ef10dee 100644
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -1124,12 +1124,14 @@ type_identifier         :       STRING  { $$ = $1; }
 
 hook_spec              :       TYPE            STRING          HOOK            
STRING          dev_spec        PRIORITY        prio_spec
                        {
-                               $<chain>0->type         = 
xstrdup(chain_type_name_lookup($2));
-                               if ($<chain>0->type == NULL) {
+                               const char *chain_type = 
chain_type_name_lookup($2);
+
+                               if (chain_type == NULL) {
                                        erec_queue(error(&@2, "unknown chain 
type %s", $2),
                                                   state->msgs);
                                        YYERROR;
                                }
+                               $<chain>0->type         = xstrdup(chain_type);
                                xfree($2);
 
                                $<chain>0->hookstr      = 
chain_hookname_lookup($4);
-- 
2.5.5


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