Re: [PATCH RFC 1/4] powerpc/crash_dump: check ioremap_cache() in copy_oldmem_page()

[Geert Uytterhoeven]

On Thu, 12 Nov 2026 at 17:39, Christian Brauner <brauner@xxxxxxxxxx> wrote:
> copy_oldmem_page() maps a page of the old kernel that isn't in the
> linear mapping with ioremap_cache() and copies from it without checking
> whether the mapping worked. If it didn't, the copy reads from an offset
> into the NULL page. That oopses unless the copy happens to be a user
> copy, whose exception table entries turn the fault into a short copy.
>
> Return -ENOMEM like the other architectures do. read_from_oldmem()
> turns that into -EFAULT like any other short copy.
>
> Reported-by: Chris Mason <mason@xxxxxxxxxx>
> Fixes: 54c32021eb6f ("[PATCH] powerpc: Add arch-dependent copy_oldmem_page")
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Breno Leitao <leitao@xxxxxxxxxx>
> Signed-off-by: Christian Brauner (Amutable) <brauner@xxxxxxxxxx>

Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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