netlink: invert error code in netlink_set_err()
The callers of netlink_set_err() currently pass a negative value
as parameter for the error code. However, sk->sk_err wants a
positive error value. Without this patch, skb_recv_datagram() called
by netlink_recvmsg() may return a positive value to report an error.
Another choice to fix this is to change callers to pass a positive
error value, but this seems a bit inconsistent and error prone
to me. Indeed, the callers of netlink_set_err() assumed that the
(usual) negative value for error codes was fine before this patch :).
This patch also includes some documentation in docbook format
for netlink_set_err() to avoid this sort of confusion.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 9eb895c..3ae3cb8 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1084,6 +1084,13 @@
return 0;
}
+/**
+ * netlink_set_err - report error to broadcast listeners
+ * @ssk: the kernel netlink socket, as returned by netlink_kernel_create()
+ * @pid: the PID of a process that we want to skip (if any)
+ * @groups: the broadcast group that will notice the error
+ * @code: error code, must be negative (as usual in kernelspace)
+ */
void netlink_set_err(struct sock *ssk, u32 pid, u32 group, int code)
{
struct netlink_set_err_data info;
@@ -1093,7 +1100,8 @@
info.exclude_sk = ssk;
info.pid = pid;
info.group = group;
- info.code = code;
+ /* sk->sk_err wants a positive error value */
+ info.code = -code;
read_lock(&nl_table_lock);