Affected: Linux, Siemens SIMATIC CN 4100

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

MIPS: Don't crash in stack_top() for tasks without ABI or vDSO

Not all tasks have an ABI associated or vDSO mapped, for example kthreads never do. If such a task ever ends up calling stack_top(), it will derefence the NULL ABI pointer and crash.

This can for example happen when using kunit:

mips_stack_top+0x28/0xc0 arch_pick_mmap_layout+0x190/0x220 kunit_vm_mmap_init+0xf8/0x138 __kunit_add_resource+0x40/0xa8 kunit_vm_mmap+0x88/0xd8 usercopy_test_init+0xb8/0x240 kunit_try_run_case+0x5c/0x1a8 kunit_generic_run_threadfn_adapter+0x28/0x50 kthread+0x118/0x240 ret_from_kernel_thread+0x14/0x1c

Only dereference the ABI point if it is set.

The GIC page is also included as it is specific to the vDSO. Also move the randomization adjustment into the same conditional.