Re: [PATCH v3 3/5] RISC-V: Improve init_resources

Geert Uytterhoeven
2021-04-06T07:20:36Z

Hi Nick,

Thanks for your patch!

On Mon, Apr 5, 2021 at 10:57 AM Nick Kossifidis <mick@ics.forth.gr> wrote:
> * Kernel region is always present and we know where it is, no
> need to look for it inside the loop, just ignore it like the
> rest of the reserved regions within system's memory.
>
> * Don't call memblock_free inside the loop, if called it'll split
> the region of pre-allocated resources in two parts, messing things
> up, just re-use the previous pre-allocated resource and free any
> unused resources after both loops finish.
>
> * memblock_alloc may add a region when called, so increase the
> number of pre-allocated regions by one to be on the safe side
> (reported and patched by Geert Uytterhoeven)
>
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

Where does this SoB come from?

> Signed-off-by: Nick Kossifidis <mick@ics.forth.gr>

> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c

> @@ -129,53 +139,42 @@ static void __init init_resources(void)
> struct resource *res = NULL;
> struct resource *mem_res = NULL;
> size_t mem_res_sz = 0;
> - int ret = 0, i = 0;
> -
> - code_res.start = __pa_symbol(_text);
> - code_res.end = __pa_symbol(_etext) - 1;
> - code_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> -
> - rodata_res.start = __pa_symbol(__start_rodata);
> - rodata_res.end = __pa_symbol(__end_rodata) - 1;
> - rodata_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> -
> - data_res.start = __pa_symbol(_data);
> - data_res.end = __pa_symbol(_edata) - 1;
> - data_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> + int num_resources = 0, res_idx = 0;
> + int ret = 0;
>
> - bss_res.start = __pa_symbol(__bss_start);
> - bss_res.end = __pa_symbol(__bss_stop) - 1;
> - bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> + /* + 1 as memblock_alloc() might increase memblock.reserved.cnt */
> + num_resources = memblock.memory.cnt + memblock.reserved.cnt + 1;
> + res_idx = num_resources - 1;
>
> - mem_res_sz = (memblock.memory.cnt + memblock.reserved.cnt) * sizeof(*mem_res);

Oh, you incorporated my commit ce989f1472ae350e ("RISC-V: Fix out-of-bounds
accesses in init_resources()") (from v5.12-rc4) into your patch.
Why? This means your patch does not apply against upstream.

> + mem_res_sz = num_resources * sizeof(*mem_res);
> mem_res = memblock_alloc(mem_res_sz, SMP_CACHE_BYTES);
> if (!mem_res)
> panic("%s: Failed to allocate %zu bytes\n", __func__, mem_res_sz);

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds