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/reference/C/CONTRIB/OR_PRACTICAL_C/14_15.c

#define X_SIZE 60
#define Y_SIZE 32

int matrix[X_SIZE][Y_SIZE];

void init_matrix(void)
{
    register int x,y;    /* current element to zero */

    for (y = 0; y < Y_SIZE; y++) {
        for (x = 0; x < X_SIZE; x++) {
            matrix[x][y] = -1;
        }
    }
}