syzbot triggered the WARN_ON in netlink_ack testing the bad_attr value.
The problem is that netlink_rcv_skb loops over the skb repeatedly invoking
the callback and without resetting the extack leaving potentially stale
data. Initializing each time through avoids the WARN_ON.
Fixes: 2d4bc93368f5a ("netlink: extended ACK reporting")
Reported-by: [email protected]
Signed-off-by: David Ahern <[email protected]>
---
net/netlink/af_netlink.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 972bfe113043..ee8252d7b3d4 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2417,7 +2417,7 @@ int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct
sk_buff *,
struct nlmsghdr *,
struct netlink_ext_ack *))
{
- struct netlink_ext_ack extack = {};
+ struct netlink_ext_ack extack;
struct nlmsghdr *nlh;
int err;
@@ -2438,6 +2438,7 @@ int netlink_rcv_skb(struct sk_buff *skb, int (*cb)(struct
sk_buff *,
if (nlh->nlmsg_type < NLMSG_MIN_TYPE)
goto ack;
+ memset(&extack, 0, sizeof(extack));
err = cb(skb, nlh, &extack);
if (err == -EINTR)
goto skip;
--
2.11.0
