sched: address a potential NULL pointer dereference in the GRED scheduler.

In the Linux kernel, the following vulnerability has been resolved:

sched: address a potential NULL pointer dereference in the GRED scheduler.

If kzalloc in gred_init returns a NULL pointer, the code follows the

error handling path, invoking gred_destroy. This, in turn, calls

gred_offload, where memset could receive a NULL pointer as input,

potentially leading to a kernel crash.

When table->opt is NULL in gred_init(), gred_change_table_def()

is not called yet, so it is not necessary to call ->ndo_setup_tc()

in gred_offload().