src: invalid read when importing chain name

Use strlen(), otherwise mpz_import_data() reads too much beyond the real
chain string. Valgrind reports the following error:

==2759== Invalid read of size 1
==2759==    at 0x67D68D6: __gmpz_import (in /usr/lib/x86_64-linux-gnu/libgmp.so.10.3.2)
==2759==    by 0x4E79467: mpz_import_data (gmputil.c:133)
==2759==    by 0x4E60A12: constant_expr_alloc (expression.c:375)
==2759==    by 0x4E8ED65: nft_parse (parser_bison.y:3825)
==2759==    by 0x4E7E850: nft_parse_bison_buffer (libnftables.c:357)
==2759==    by 0x4E7E850: nft_run_cmd_from_buffer (libnftables.c:424)
==2759==    by 0x1095D4: main (in /tmp/a.out)
==2759==  Address 0x6ee1b4a is 0 bytes after a block of size 10 alloc'd
==2759==    at 0x4C2BBAF: malloc (vg_replace_malloc.c:299)
==2759==    by 0x59FD3B9: strdup (strdup.c:42)
==2759==    by 0x4E7963D: xstrdup (utils.c:75)
==2759==    by 0x4E9C233: nft_lex (scanner.l:626)
==2759==    by 0x4E8E382: nft_parse (parser_bison.c:5297)
==2759==    by 0x4E7E850: nft_parse_bison_buffer (libnftables.c:357)
==2759==    by 0x4E7E850: nft_run_cmd_from_buffer (libnftables.c:424)

Fixes: f1e8a129ee42 ("src: Introduce chain_expr in jump and goto statements")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/src/netlink.c b/src/netlink.c
index ef12cb016b1d9389a7e4336910436330bf5b873d..e9779684ac0974eaa39cd084aaaf7fc8db0bf031 100644 (file)
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -265,8 +265,8 @@ static struct expr *netlink_alloc_verdict(const struct location *loc,
        case NFT_GOTO:
                chain = constant_expr_alloc(loc, &string_type,
                                            BYTEORDER_HOST_ENDIAN,
-                                           NFT_CHAIN_MAXNAMELEN *
-                                           BITS_PER_BYTE, nld->chain);
+                                           strlen(nld->chain) * BITS_PER_BYTE,
+                                           nld->chain);
                break;
        default:
                chain = NULL;

diff --git a/src/parser_bison.y b/src/parser_bison.y
index 8026708ed8591b7b18637900878f91341f645209..5ffb5cc221453098c93f86d41578a83bb874417e 100644 (file)
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -3824,8 +3824,8 @@ chain_expr                :       variable_expr
                        {
                                $$ = constant_expr_alloc(&@$, &string_type,
                                                         BYTEORDER_HOST_ENDIAN,
-                                                        NFT_CHAIN_MAXNAMELEN *
-                                                        BITS_PER_BYTE, $1);
+                                                        strlen($1) * BITS_PER_BYTE,
+                                                        $1);
                        }
                        ;