nft: fix out of bound memory copy

Valgrind reports an invalid read after a memory block:

==11114== Invalid read of size 8
==11114==    at 0x4C2DB02: memcpy@@GLIBC_2.14 (mc_replace_strmem.c:877)
==11114==    by 0x41788E: add_match (nft.c:781)
==11114==    by 0x41B54C: nft_ipv4_add (nft-ipv4.c:72)
==11114==    by 0x415DF2: nft_rule_new.isra.2 (nft.c:945)
==11114==    by 0x418ACE: nft_rule_append (nft.c:1000)
==11114==    by 0x413A92: add_entry.isra.6 (xtables.c:424)
==11114==    by 0x4152DE: do_commandx (xtables.c:1184)
==11114==    by 0x4134E8: xtables_main (xtables-standalone.c:72)
==11114==    by 0x5B87994: (below main) (libc-start.c:260)
==11114==  Address 0x61399e8 is 8 bytes after a block of size 48 alloc'd
==11114==    at 0x4C2B514: calloc (vg_replace_malloc.c:593)
==11114==    by 0x52448C8: xtables_calloc (xtables.c:272)
==11114==    by 0x410AC2: command_default (xshared.c:150)
==11114==    by 0x4149A2: do_commandx (xtables.c:1075)
==11114==    by 0x4134E8: xtables_main (xtables-standalone.c:72)
==11114==    by 0x5B87994: (below main) (libc-start.c:260)

m->u.match_size also contains the size of the xt_entry_match structure.
Fix also the target path which is very similar.

Reported-by: Ana Rey Botello <anarey@gmail.com>
Tested-by: Ana Rey Botello <anarey@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/iptables/nft.c b/iptables/nft.c
index 01e026404a8d68feda24711d118ce91d3357f844..2135b04c8013e7ca2423768e553194af3c62292a 100644 (file)
--- a/iptables/nft.c
+++ b/iptables/nft.c
@@ -776,7 +776,7 @@ static int __add_match(struct nft_rule_expr *e, struct xt_entry_match *m)
        if (info == NULL)
                return -ENOMEM;
 
-       memcpy(info, m->data, m->u.match_size);
+       memcpy(info, m->data, m->u.match_size - sizeof(*m));
        nft_rule_expr_set(e, NFT_EXPR_MT_INFO, info, m->u.match_size - sizeof(*m));
 
        return 0;
@@ -799,20 +799,17 @@ int add_match(struct nft_rule *r, struct xt_entry_match *m)
 
 static int __add_target(struct nft_rule_expr *e, struct xt_entry_target *t)
 {
-       void *info = NULL;
+       void *info;
 
        nft_rule_expr_set(e, NFT_EXPR_TG_NAME, t->u.user.name,
                          strlen(t->u.user.name));
        nft_rule_expr_set_u32(e, NFT_EXPR_TG_REV, t->u.user.revision);
 
-       if (info == NULL) {
-               info = calloc(1, t->u.target_size);
-               if (info == NULL)
-                       return -ENOMEM;
-
-               memcpy(info, t->data, t->u.target_size);
-       }
+       info = calloc(1, t->u.target_size);
+       if (info == NULL)
+               return -ENOMEM;
 
+       memcpy(info, t->data, t->u.target_size - sizeof(*t));
        nft_rule_expr_set(e, NFT_EXPR_TG_INFO, info, t->u.target_size - sizeof(*t));
 
        return 0;