[PATCH] net/core/dev_ioctl: avoid invoking modprobe with empty ifr_name

[Song Chen]

dev_ioctl handles requests from user space if a process calls
ioctl(sockfd, SIOCGIFINDEX, &ifr). However, if this user space
process doesn't have interface name well specified, dev_ioctl
doesn't give it an essential check, as a result, dev_load will
invoke modprobe with a nonsense module name if the user happens
to be sys admin or root, see following code in dev_load:

    no_module = !dev;
    if (no_module && capable(CAP_NET_ADMIN))
        no_module = request_module("netdev-%s", name);
    if (no_module && capable(CAP_SYS_MODULE))
        request_module("%s", name);

This patch checks if ifr_name is empty at the beginning, reduces
the overhead of calling modprobe.

Signed-off-by: Song Chen <chensong_2000@xxxxxx>
---
 net/core/dev_ioctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index 473c437b6b53..1371269f17d5 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -676,6 +676,9 @@ int dev_ioctl(struct net *net, unsigned int cmd, struct ifreq *ifr,
 	if (cmd == SIOCGIFNAME)
 		return dev_ifname(net, ifr);
 
+	if (ifr->ifr_name[0] == '\0')
+		return -EINVAL;
+
 	ifr->ifr_name[IFNAMSIZ-1] = 0;
 
 	colon = strchr(ifr->ifr_name, ':');
-- 
2.25.1