riscv: kprobe: Fixup kernel panic when probing an illegal position

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

riscv: kprobe: Fixup kernel panic when probing an illegal position

The kernel would panic when probed for an illegal position. eg:

(CONFIG_RISCV_ISA_C=n)

echo 'p:hello kernel_clone+0x16 a0=%a0' >> kprobe_events

echo 1 > events/kprobes/hello/enable

cat trace

Kernel panic - not syncing: stack-protector: Kernel stack

is corrupted in: __do_sys_newfstatat+0xb8/0xb8

CPU: 0 PID: 111 Comm: sh Not tainted

6.2.0-rc1-00027-g2d398fe49a4d #490

Hardware name: riscv-virtio,qemu (DT)

Call Trace:

[<ffffffff80007268>] dump_backtrace+0x38/0x48

[<ffffffff80c5e83c>] show_stack+0x50/0x68

[<ffffffff80c6da28>] dump_stack_lvl+0x60/0x84

[<ffffffff80c6da6c>] dump_stack+0x20/0x30

[<ffffffff80c5ecf4>] panic+0x160/0x374

[<ffffffff80c6db94>] generic_handle_arch_irq+0x0/0xa8

[<ffffffff802deeb0>] sys_newstat+0x0/0x30

[<ffffffff800158c0>] sys_clone+0x20/0x30

[<ffffffff800039e8>] ret_from_syscall+0x0/0x4

---[ end Kernel panic - not syncing: stack-protector:

Kernel stack is corrupted in: __do_sys_newfstatat+0xb8/0xb8 ]---

That is because the kprobe's ebreak instruction broke the kernel's

original code. The user should guarantee the correction of the probe

position, but it couldn't make the kernel panic.

This patch adds arch_check_kprobe in arch_prepare_kprobe to prevent an

illegal position (Such as the middle of an instruction).