[PATCH V2] riscv: kprobe: Fixup kernel panic when probing an illegal position

[Björn Töpel]

guoren at kernel.org writes:

> From: Guo Ren <guoren at linux.alibaba.com>
>
> 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).
>
> Fixes: c22b0bcb1dd0 ("riscv: Add kprobes supported")
> Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren at kernel.org>
> ---
> Changelog
> V2:
>  - Fixup misaligned load (Thx Bjorn)

Reviewed-by: Björn Töpel <bjorn at kernel.org>