Re: [PATCH v2] riscv/purgatory: Do not use fortified string functions

[Conor Dooley]

On Thu, Jun 01, 2023 at 09:00:28AM -0700, 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/
> Bisected-by: "Joan Bruguera Micó" <joanbrugueram@xxxxxxxxx>
> Fixes: df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3")
> Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
> Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
> Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> Cc: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>

Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>

Thanks for the quick update Kees,
Conor.

Attachment: signature.asc
Description: PGP signature