[PATCH nft] scanner: incorrect error reporting after file inclusion

[PATCH nft] scanner: incorrect error reporting after file inclusion

[Pablo Neira Ayuso]

scanner_pop_buffer() incorrectly sets the current input descriptor. The
state->indesc_idx field actually stores the number of input descriptors
in the stack, decrement it and then update the current input descriptor
accordingly.

Fixes: 60e917fa7cb5 ("src: dynamic input_descriptor allocation")
Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1383
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 src/scanner.l | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/scanner.l b/src/scanner.l
index 4fbdcf2afa4b..99ee83559d2e 100644
--- a/src/scanner.l
+++ b/src/scanner.l
@@ -665,12 +665,29 @@ addrstring	({macaddr}|{ip4addr}|{ip6addr})
 
 %%
 
+static void scanner_push_indesc(struct parser_state *state,
+				struct input_descriptor *indesc)
+{
+	state->indescs[state->indesc_idx] = indesc;
+	state->indesc = state->indescs[state->indesc_idx++];
+}
+
+static void scanner_pop_indesc(struct parser_state *state)
+{
+	state->indesc_idx--;
+
+	if (state->indesc_idx > 0)
+		state->indesc = state->indescs[state->indesc_idx - 1];
+	else
+		state->indesc = NULL;
+}
+
 static void scanner_pop_buffer(yyscan_t scanner)
 {
 	struct parser_state *state = yyget_extra(scanner);
 
 	yypop_buffer_state(scanner);
-	state->indesc = state->indescs[--state->indesc_idx];
+	scanner_pop_indesc(state);
 }
 
 static void scanner_push_file(struct nft_ctx *nft, void *scanner,
@@ -691,8 +708,7 @@ static void scanner_push_file(struct nft_ctx *nft, void *scanner,
 	indesc->name	= xstrdup(filename);
 	init_pos(indesc);
 
-	state->indescs[state->indesc_idx] = indesc;
-	state->indesc = state->indescs[state->indesc_idx++];
+	scanner_push_indesc(state, indesc);
 	list_add_tail(&indesc->list, &state->indesc_list);
 }
 
-- 
2.11.0