Re: [coreboot] Dell Dimension 8300 reboots when grub2 cbfs module is loaded

[Martin Roth]

Thanks Andrei,

Vladimir, what do you think?

Martin

On Sun, Nov 1, 2015 at 7:53 AM, Andrei Borzenkov <address@hidden> wrote:
> I was debugging problem reported by user on Dell Dimension 8300 - it
> rebooted when doing "ls -l". It turned out, the problem was triggered by
> loading cbfs which probed for header. System has 2GB memory, and attempt to
> read from address 0xffffffff caused instant reboot. 0xffffffff was returned
> by read from non-existing address 0xfffffffc.
>
> The proof of concept patch below avoids it, but I wonder what the proper fix
> is.
>
> diff --git a/grub-core/fs/cbfs.c b/grub-core/fs/cbfs.c
> index a34eb88..a5a2fde 100644
> --- a/grub-core/fs/cbfs.c
> +++ b/grub-core/fs/cbfs.c
> @@ -344,8 +344,9 @@ init_cbfsdisk (void)
>
>    ptr = *(grub_uint32_t *) 0xfffffffc;
>    head = (struct cbfs_header *) (grub_addr_t) ptr;
> +  grub_dprintf ("cbfs", "head=%p\n", head);
>
> -  if (!validate_head (head))
> +  if (0xffffffff - ptr < sizeof (*head) || !validate_head (head))
>      return;
>
>    cbfsdisk_size = ALIGN_UP (grub_be_to_cpu32 (head->romsize),
>
>
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