[PATCH nft 4/6] parser: reject zero-length interface names

[Florian Westphal <fw@strlen.de>]

device "" results in an assertion during evaluation.
Before:
nft: expression.c:426: constant_expr_alloc: Assertion `(((len) + (8) - 1) / (8)) > 0' failed.
After:
zero_length_devicename_assert:3:42-49: Error: you cannot set an empty interface name
type filter hook ingress device""lo" priority -1
                         ^^^^^^^^
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 src/parser_bison.y                            | 36 ++++++++++++++++---
 .../nft-f/zero_length_devicename_assert       |  5 +++
 2 files changed, 36 insertions(+), 5 deletions(-)
 create mode 100644 tests/shell/testcases/bogons/nft-f/zero_length_devicename_assert

diff --git a/src/parser_bison.y b/src/parser_bison.y
index f5f6bf04d064..d5a2f85387cb 100644
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -144,6 +144,33 @@ static bool already_set(const void *attr, const struct location *loc,
 	return true;
 }
 
+static struct expr* ifname_expr_alloc(const struct location *location,
+				      struct list_head *queue,
+				      const char *name)
+{
+	unsigned int length = strlen(name);
+	struct expr *expr;
+
+	if (length == 0) {
+		xfree(name);
+		erec_queue(error(location, "empty interface name"), queue);
+		return NULL;
+	}
+
+	if (length > 16) {
+		xfree(name);
+		erec_queue(error(location, "interface name too long"), queue);
+		return NULL;
+	}
+
+	expr = constant_expr_alloc(location, &ifname_type, BYTEORDER_HOST_ENDIAN,
+				   length * BITS_PER_BYTE, name);
+
+	xfree(name);
+
+	return expr;
+}
+
 #define YYLLOC_DEFAULT(Current, Rhs, N)	location_update(&Current, Rhs, N)
 
 #define symbol_value(loc, str) \
@@ -2664,12 +2691,11 @@ int_num			:	NUM			{ $$ = $1; }
 
 dev_spec		:	DEVICE	string
 			{
-				struct expr *expr;
+				struct expr *expr = ifname_expr_alloc(&@$, state->msgs, $2);
+
+				if (!expr)
+					YYERROR;
 
-				expr = constant_expr_alloc(&@$, &string_type,
-							   BYTEORDER_HOST_ENDIAN,
-							   strlen($2) * BITS_PER_BYTE, $2);
-				xfree($2);
 				$$ = compound_expr_alloc(&@$, EXPR_LIST);
 				compound_expr_add($$, expr);
 
diff --git a/tests/shell/testcases/bogons/nft-f/zero_length_devicename_assert b/tests/shell/testcases/bogons/nft-f/zero_length_devicename_assert
new file mode 100644
index 000000000000..84f330730fce
--- /dev/null
+++ b/tests/shell/testcases/bogons/nft-f/zero_length_devicename_assert
@@ -0,0 +1,5 @@
+table ip x {
+        chain Main_Ingress1 {
+                type filter hook ingress device""lo" priority -1
+	}
+}
-- 
2.39.3