Re: [PATCH] x86/purgatory: Do not use fortified string functions

[Thorsten Leemhuis]

Kees, thx for looking into this.

Joan, thx for bisecting. I should have done this earlier myself...

On 31.05.23 02:33, Kees Cook wrote:
> With the addition of -fstrict-flex-arrays=3, struct sha256_state's
> trailing array is no longer ignored by CONFIG_FORTIFY_SOURCE:
> 
> struct sha256_state {
>         u32 state[SHA256_DIGEST_SIZE / 4];
>         u64 count;
>         u8 buf[SHA256_BLOCK_SIZE];
> };
> 
> This means that the memcpy() calls with "buf" as a destination in
> sha256.c's code will attempt to perform run-time bounds checking, which
> could lead to calling missing functions, specifically a potential
> WARN_ONCE, which isn't callable from purgatory.
> 
> Reported-by: Thorsten Leemhuis <linux@xxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/lkml/175578ec-9dec-7a9c-8d3a-43f24ff86b92@xxxxxxxxxxxxx/

Did a test build and booted it in a Vm, everything seems fine. So thx
again and feel free to add:

Tested-by: Thorsten Leemhuis <linux@xxxxxxxxxxxxx>

Ciao, Thorsten