netlink: put module reference if dump start fails

Before, if cb->start() failed, the module reference would never be put,
because cb->cb_running is intentionally false at this point. Users are
generally annoyed by this because they can no longer unload modules that
leak references. Also, it may be possible to tediously wrap a reference
counter back to zero, especially since module.c still uses atomic_inc
instead of refcount_inc.

This patch expands the error path to simply call module_put if
cb->start() fails.

Fixes: 41c87425a1ac ("netlink: do not set cb_running if dump's start() errs")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 2ad445c1d27ccda471132e035229188b77a579eb..07e8478068f0a1fafc0b41bb939ed508d40e3f21 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2308,7 +2308,7 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
        if (cb->start) {
                ret = cb->start(cb);
                if (ret)
-                       goto error_unlock;
+                       goto error_put;
        }
 
        nlk->cb_running = true;
@@ -2328,6 +2328,8 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
         */
        return -EINTR;
 
+error_put:
+       module_put(control->module);
 error_unlock:
        sock_put(sk);
        mutex_unlock(nlk->cb_mutex);