Re: [PATCH 3/7] builtin/bugreport.c: avoid size_t overflow

From: Junio C Hamano <gitster@pobox.com>
Date: Aug 1, 2022, 22:18 UTC
Message-ID: <xmqqpmhjmwu4.fsf@gitster.g>
In-Reply-To: <e8abfdfa892f5670ed411ed6daef26a4ffa1bfe6.1659388498.git.gitgitgadget@gmail.com>

"Victoria Dye via GitGitGadget" <gitgitgadget@gmail.com> writes:

Show 7 quoted lines

> From: Victoria Dye <vdye@github.com>
>
> Avoid size_t overflow when reporting the available disk space in
> 'get_disk_info' by casting the block size and available block count to
> 'uint64_t' before multiplying them. Without this change, 'st_mult' would
> (correctly) report size_t overflow on 32-bit systems at or exceeding 2^32
> bytes of available space.

Sane. But shouldn't the cast be to off_t, which is what strbuf_humanise_bytes() takes anyway?

Show 19 quoted lines

>
> Signed-off-by: Victoria Dye <vdye@github.com>
> ---
>  builtin/bugreport.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/builtin/bugreport.c b/builtin/bugreport.c
> index 35b1fc48bf1..720889a37ad 100644
> --- a/builtin/bugreport.c
> +++ b/builtin/bugreport.c
> @@ -258,7 +258,7 @@ static int get_disk_info(struct strbuf *out)
>  	}
>  
>  	strbuf_addf(out, "Available space on '%s': ", buf.buf);
> -	strbuf_humanise_bytes(out, st_mult(stat.f_bsize, stat.f_bavail));
> +	strbuf_humanise_bytes(out, (uint64_t)stat.f_bsize * (uint64_t)stat.f_bavail);
>  	strbuf_addf(out, " (mount flags 0x%lx)\n", stat.f_flag);
>  	strbuf_release(&buf);
>  #endif