net: don't unnecessarily load kernel modules in dev_ioctl()

Starting with v4.16-rc1 we've been seeing a higher than usual number
of requests for the kernel to load networking modules, even on events
which shouldn't trigger a module load (e.g. ioctl(TCGETS)).  Stephen
Smalley suggested the problem may lie in commit 44c02a2c3dc5
("dev_ioctl(): move copyin/copyout to callers") which moves changes
the network dev_ioctl() function to always call dev_load(),
regardless of the requested ioctl.

This patch moves the dev_load() calls back into the individual ioctls
while preserving the rest of the original patch.

Reported-by: Dominick Grift <dac.override@gmail.com>
Suggested-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index 0ab1af0..a04e1e8 100644 (file)
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -402,8 +402,6 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr, bool *need_c
        if (colon)
                *colon = 0;
 
-       dev_load(net, ifr->ifr_name);
-
        /*
         *      See which interface the caller is talking about.
         */
@@ -423,6 +421,7 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr, bool *need_c
        case SIOCGIFMAP:
        case SIOCGIFINDEX:
        case SIOCGIFTXQLEN:
+               dev_load(net, ifr->ifr_name);
                rcu_read_lock();
                ret = dev_ifsioc_locked(net, ifr, cmd);
                rcu_read_unlock();
@@ -431,6 +430,7 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr, bool *need_c
                return ret;
 
        case SIOCETHTOOL:
+               dev_load(net, ifr->ifr_name);
                rtnl_lock();
                ret = dev_ethtool(net, ifr);
                rtnl_unlock();
@@ -447,6 +447,7 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr, bool *need_c
        case SIOCGMIIPHY:
        case SIOCGMIIREG:
        case SIOCSIFNAME:
+               dev_load(net, ifr->ifr_name);
                if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
                        return -EPERM;
                rtnl_lock();
@@ -494,6 +495,7 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr, bool *need_c
                /* fall through */
        case SIOCBONDSLAVEINFOQUERY:
        case SIOCBONDINFOQUERY:
+               dev_load(net, ifr->ifr_name);
                rtnl_lock();
                ret = dev_ifsioc(net, ifr, cmd);
                rtnl_unlock();
@@ -518,6 +520,7 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr, bool *need_c
                    cmd == SIOCGHWTSTAMP ||
                    (cmd >= SIOCDEVPRIVATE &&
                     cmd <= SIOCDEVPRIVATE + 15)) {
+                       dev_load(net, ifr->ifr_name);
                        rtnl_lock();
                        ret = dev_ifsioc(net, ifr, cmd);
                        rtnl_unlock();