expr: fix buffer overflows in data value setters

The data value setters memcpy() to a fixed-size buffer, but its very easy
to make nft pass too-larger values.  Example:
  @th,160,1272 gt 0

ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60b000[..]

Truncate the copy instead of corrupting the heap.
This needs additional fixes on nft side to reject such statements with a
proper error message.

Signed-off-by: Florian Westphal <fw@strlen.de>

1 files changed, 1 insertions, 3 deletions

diff --git a/src/expr/cmp.c b/src/expr/cmp.c
index f9d15bb..1d396e8 100644
--- a/src/expr/cmp.c
+++ b/src/expr/cmp.c
@@ -42,9 +42,7 @@ nftnl_expr_cmp_set(struct nftnl_expr *e, uint16_t type,
 		memcpy(&cmp->op, data, sizeof(cmp->op));
 		break;
 	case NFTNL_EXPR_CMP_DATA:
-		memcpy(&cmp->data.val, data, data_len);
-		cmp->data.len = data_len;
-		break;
+		return nftnl_data_cpy(&cmp->data, data, data_len);
 	default:
 		return -1;
 	}