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Subject[PATCH 3.18 08/29] netfilter: x_tables: initialise match/target check parameter struct
Date
3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

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>

---
net/bridge/netfilter/ebtables.c | 2 ++
net/ipv4/netfilter/ip_tables.c | 1 +
net/ipv6/netfilter/ip6_tables.c | 1 +
3 files changed, 4 insertions(+)

--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -699,6 +699,8 @@ ebt_check_entry(struct ebt_entry *e, str
}
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;
--- 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, st
struct xt_entry_match *ematch;

j = 0;
+ memset(&mtpar, 0, sizeof(mtpar));
mtpar.net = net;
mtpar.table = name;
mtpar.entryinfo = &e->ip;
--- 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, s
struct xt_entry_match *ematch;

j = 0;
+ memset(&mtpar, 0, sizeof(mtpar));
mtpar.net = net;
mtpar.table = name;
mtpar.entryinfo = &e->ipv6;

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