Re: [PATCH v2] vt: Replace strlcpy with strscpy

[Kees Cook]

On Tue, Sep 19, 2023 at 07:21:56PM +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first and returns the size of
> the source string, not the destination string, which can be accidentally
> misused [1].
> 
> The copy_to_user() call uses @len returned from strlcpy() directly
> without checking its value. This could potentially lead to read
> overflow. There is no existing bug since @len is always guaranteed to be
> greater than hardcoded strings in @func_table[kb_func]. But as written
> it is very fragile and specifically uses a strlcpy() result without sanity
> checking and using it to copy to userspace.
> 
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeems@xxxxxxxxxx>
> ---
> v2:
>  * Return -ENOSPC instead of -EFAULT in case of truncation.
>  * Update commit log to clarify that there is no exploitable bug but instead the code uses a fragile anti-pattern.

Changes look good. Thanks!

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-- 
Kees Cook