net: dsa: fix unbalanced dsa_switch_tree reference counting

_dsa_register_switch() gets a dsa_switch_tree object either via
dsa_get_dst() or via dsa_add_dst(). Former path does not increase kref
in returned object (resulting into caller not owning a reference),
while later path does create a new object (resulting into caller owning
a reference).

The rest of _dsa_register_switch() assumes that it owns a reference, and
calls dsa_put_dst().

This causes a memory breakage if first switch in the tree initialized
successfully, but second failed to initialize. In particular, freed
dsa_swith_tree object is left referenced by switch that was initialized,
and later access to sysfs attributes of that switch cause OOPS.

To fix, need to add kref_get() call to dsa_get_dst().

Fixes: 83c0afaec7b7 ("net: dsa: Add new binding implementation")
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

path: root/dev.h

#ifndef DEV_H
#define DEV_H

#include <sys/socket.h>
#include "built_in.h"

extern int device_mtu(const char *ifname);
extern int device_address(const char *ifname, int af, struct sockaddr_storage *ss);
extern int device_ifindex(const char *ifname);
extern short device_get_flags(const char *ifname);
extern void device_set_flags(const char *ifname, const short flags);
extern int device_up_and_running(char *ifname);
extern u32 device_bitrate(const char *ifname);

#endif /* DEV_H */