Commit 47733f9d authored Aug 15, 2020 by Cong Wang Committed by David S. Miller Aug 16, 2020

tipc: fix uninit skb->data in tipc_nl_compat_dumpit()



__tipc_nl_compat_dumpit() has two callers, and it expects them to
pass a valid nlmsghdr via arg->data. This header is artificial and
crafted just for __tipc_nl_compat_dumpit().

tipc_nl_compat_publ_dump() does so by putting a genlmsghdr as well
as some nested attribute, TIPC_NLA_SOCK. But the other caller
tipc_nl_compat_dumpit() does not, this leaves arg->data uninitialized
on this call path.

Fix this by just adding a similar nlmsghdr without any payload in
tipc_nl_compat_dumpit().

This bug exists since day 1, but the recent commit 6ea67769
("net: tipc: prepare attrs in __tipc_nl_compat_dumpit()") makes it
easier to appear.

Reported-and-tested-by:  <syzbot+0e7181deafa7e0b79923@syzkaller.appspotmail.com>
Fixes: d0796d1e ("tipc: convert legacy nl bearer dump to nl compat")
Cc: Jon Maloy <jmaloy@redhat.com>
Cc: Ying Xue <ying.xue@windriver.com>
Cc: Richard Alpe <richard.alpe@ericsson.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 8c26544f

net/tipc/netlink_compat.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -275,8 +275,9 @@ err_out:
		static int tipc_nl_compat_dumpit(struct tipc_nl_compat_cmd_dump *cmd,
		struct tipc_nl_compat_msg *msg)
		{
		int err;
		struct nlmsghdr *nlh;
		struct sk_buff *arg;
		int err;

		if (msg->req_type && (!msg->req_size \|\|
		!TLV_CHECK_TYPE(msg->req, msg->req_type)))
		@@ -305,6 +306,15 @@ static int tipc_nl_compat_dumpit(struct tipc_nl_compat_cmd_dump *cmd,
		return -ENOMEM;
		}

		nlh = nlmsg_put(arg, 0, 0, tipc_genl_family.id, 0, NLM_F_MULTI);
		if (!nlh) {
		kfree_skb(arg);
		kfree_skb(msg->rep);
		msg->rep = NULL;
		return -EMSGSIZE;
		}
		nlmsg_end(arg, nlh);

		err = __tipc_nl_compat_dumpit(cmd, msg, arg);
		if (err) {
		kfree_skb(msg->rep);

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