Re: [PATCH 2/2] tracing/kprobes: handle userspace access on unified probes

[Greg KH <greg@kroah.com>]

On Mon, Mar 29, 2021 at 01:59:48PM +0300, Zidenberg, Tsahi wrote:
> 
> commit 9de1fec50b23117f0a19f7609cc837ca72e764a6 upstream.
> 
> This is an adaptation of parts from the above commit to kernel 5.4.
> 
> Allow Kprobes to access userspace data correctly in architectures with no
> overlap between kernel and userspace addresses.
> 
> Cc: <stable@vger.kernel.org> # 5.4.x
> Signed-off-by: Tsahi Zidenberg <tsahee@amazon.com>
> ---
>  kernel/trace/trace_kprobe.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 233322c77b76..cbd72a1c9530 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1043,6 +1043,11 @@ fetch_store_strlen(unsigned long addr)
>      int ret, len = 0;
>      u8 c;
>  
> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> +    if (addr < TASK_SIZE)
> +        return fetch_store_strlen_user(addr);
> +#endif
> +
>      do {
>          ret = probe_kernel_read(&c, (u8 *)addr + len, 1);
>          len++;
> @@ -1071,6 +1076,11 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
>      void *__dest;
>      long ret;
>  
> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> +    if (addr < TASK_SIZE)
> +        return fetch_store_string_user(addr, dest, base);
> +#endif
> +
>      if (unlikely(!maxlen))
>          return -ENOMEM;
>  
> @@ -1114,6 +1124,11 @@ fetch_store_string_user(unsigned long addr, void *dest, void *base)
>  static nokprobe_inline int
>  probe_mem_read(void *dest, void *src, size_t size)
>  {
> +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
> +    if ((unsigned long)src < TASK_SIZE)
> +        return probe_mem_read_user(dest, src, size);
> +#endif
> +
>      return probe_kernel_read(dest, src, size);
>  }
>  
> -- 
> 2.25.1

What problem is this fixing?

thanks,

greg k-h