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netfilter: x_tables: initialise match/target check parameter struct

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syzbot reports following splat:

BUG: KMSAN: uninit-value in ebt_stp_mt_check+0x24b/0x450
 net/bridge/netfilter/ebt_stp.c:162
 ebt_stp_mt_check+0x24b/0x450 net/bridge/netfilter/ebt_stp.c:162
 xt_check_match+0x1438/0x1650 net/netfilter/x_tables.c:506
 ebt_check_match net/bridge/netfilter/ebtables.c:372 [inline]
 ebt_check_entry net/bridge/netfilter/ebtables.c:702 [inline]

The uninitialised access is
   xt_mtchk_param->nft_compat

... which should be set to 0.
Fix it by zeroing the struct beforehand, same for tgchk.

ip(6)tables targetinfo uses c99-style initialiser, so no change
needed there.

Reported-by: syzbot+da4494182233c23a5fcf@syzkaller.appspotmail.com
Fixes: 55917a21d0 ("netfilter: x_tables: add context to know if extension runs from nft_compat")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2018-06-07 21:34:43 +02:00 committed by Pablo Neira Ayuso
parent 64e6dd1fb2
commit c568503ef0
3 changed files with 4 additions and 0 deletions
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2
net/bridge/netfilter/ebtables.c
View File

@ -700,6 +700,8 @@ ebt_check_entry(struct ebt_entry *e, struct net *net,
}
i = 0;
memset(&mtpar, 0, sizeof(mtpar));
memset(&tgpar, 0, sizeof(tgpar));
mtpar.net = tgpar.net = net;
mtpar.table = tgpar.table = name;
mtpar.entryinfo = tgpar.entryinfo = e;

1
net/ipv4/netfilter/ip_tables.c
View File

@ -531,6 +531,7 @@ find_check_entry(struct ipt_entry *e, struct net *net, const char *name,
return -ENOMEM;
j = 0;
memset(&mtpar, 0, sizeof(mtpar));
mtpar.net = net;
mtpar.table = name;
mtpar.entryinfo = &e->ip;

1
net/ipv6/netfilter/ip6_tables.c
View File

@ -551,6 +551,7 @@ find_check_entry(struct ip6t_entry *e, struct net *net, const char *name,
return -ENOMEM;
j = 0;
memset(&mtpar, 0, sizeof(mtpar));
mtpar.net = net;
mtpar.table = name;
mtpar.entryinfo = &e->ipv6;