[PATCH nft] src: invalid read when importing chain name

[Pablo Neira Ayuso <pablo@netfilter.org>]

Use strlen(), otherwise mpz_import_data() reads too much beyond the real
chain string.

==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 /home/pablo/asuntos/netfilter/nftables-bugs/nft7/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>
---
 src/netlink.c      | 4 ++--
 src/parser_bison.y | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/netlink.c b/src/netlink.c
index ef12cb016b1d..e9779684ac09 100644
--- 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 8026708ed859..5ffb5cc22145 100644
--- 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);
 			}
 			;
 
-- 
2.11.0