netfilter: x_tables: initialise match/target check parameter struct

commit c568503ef02030f169c9e19204def610a3510918 upstream.

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: 55917a21d0cc0 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 6fad6069ae24deda441b6bc645b91039008fbd0e..21bca4537ffa3ae0225039b4818bf126dbaeb27b 100644 (file)
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -699,6 +699,8 @@ 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;

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 4e40f2ec2b686175b7f430316f30b809c5932912..60ba5b0f6474c9ccfc7058d2ec3ef8283847323b 100644 (file)
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -651,6 +651,7 @@ find_check_entry(struct ipt_entry *e, struct net *net, const char *name,
        struct xt_entry_match *ematch;
 
        j = 0;
+       memset(&mtpar, 0, sizeof(mtpar));
        mtpar.net       = net;
        mtpar.table     = name;
        mtpar.entryinfo = &e->ip;

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index cb3cc2a4426a080e0fe000583c6fb355204f0b03..b4bfd07dc8ebcd970174ee8cc5546d524dc2ec16 100644 (file)
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -662,6 +662,7 @@ find_check_entry(struct ip6t_entry *e, struct net *net, const char *name,
        struct xt_entry_match *ematch;
 
        j = 0;
+       memset(&mtpar, 0, sizeof(mtpar));
        mtpar.net       = net;
        mtpar.table     = name;
        mtpar.entryinfo = &e->ipv6;