[PATCH nft] evaluate: fix stack overflow with huge priority string

[PATCH nft] evaluate: fix stack overflow with huge priority string

[Florian Westphal]

Alternative would be to refactor this and move this into the parsers
(bison, json) instead of this hidden re-parsing.

Fixes: 627c451b2351 ("src: allow variables in the chain priority specification")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 src/evaluate.c                                     | 2 +-
 tests/shell/testcases/bogons/nft-f/huge_chain_prio | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 tests/shell/testcases/bogons/nft-f/huge_chain_prio

diff --git a/src/evaluate.c b/src/evaluate.c
index 731313e08c2a..a220a8ca1809 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -4909,7 +4909,7 @@ static bool evaluate_priority(struct eval_ctx *ctx, struct prio_spec *prio,
 			NFT_NAME_MAXLEN);
 	loc = prio->expr->location;
 
-	if (sscanf(prio_str, "%s %c %d", prio_fst, &op, &prio_snd) < 3) {
+	if (sscanf(prio_str, "%255s %c %d", prio_fst, &op, &prio_snd) < 3) {
 		priority = std_prio_lookup(prio_str, family, hook);
 		if (priority == NF_IP_PRI_LAST)
 			return false;
diff --git a/tests/shell/testcases/bogons/nft-f/huge_chain_prio b/tests/shell/testcases/bogons/nft-f/huge_chain_prio
new file mode 100644
index 000000000000..41f8061a1369
--- /dev/null
+++ b/tests/shell/testcases/bogons/nft-f/huge_chain_prio
@@ -0,0 +1,5 @@
+table t {
+        chain c {
+                type filter hook input priority srcnDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD#DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD; policy accept;
+        }
+}
-- 
2.41.0