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SubjectRe: [PATCH v2] x86: selective remapping in parse_setup_data()
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On Mon, Aug 12, 2013 at 4:01 PM, Linn Crosetto <linn@hp.com> wrote:
> Type SETUP_PCI, added by setup_efi_pci(), may advertise a ROM size
> larger than early_memremap() is able to handle, which is currently
> limited to 256kB. If this occurs it leads to a NULL dereference in
> parse_setup_data().
>
> To avoid this, first remap the setup_data header, and remap the data
> only for types actually parsed in parse_setup_data(). Type SETUP_PCI is
> handled later by pcibios_add_device(), when ioremap() is available.
>
> Signed-off-by: Linn Crosetto <linn@hp.com>
> ---
> v2: add more detail to the explanation as requested by hpa
> ---
> arch/x86/kernel/setup.c | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index f8ec578..2063a49 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -423,6 +423,17 @@ static void __init reserve_initrd(void)
> }
> #endif /* CONFIG_BLK_DEV_INITRD */
>
> +static void __init remap_setup_data(u64 pa_data, u32 data_len,
> + struct setup_data **data, u32 *map_len)
> +{
> + if (data_len <= *map_len)
> + return;
> +
> + early_iounmap(*data, *map_len);
> + *data = early_memremap(pa_data, data_len);
> + *map_len = data_len;
> +}
> +
> static void __init parse_setup_data(void)
> {
> struct setup_data *data;
> @@ -432,18 +443,16 @@ static void __init parse_setup_data(void)
> while (pa_data) {
> u32 data_len, map_len;
>
> + /* The data length may be too large for early remapping,
> + remap the data only when needed. */
> map_len = max(PAGE_SIZE - (pa_data & ~PAGE_MASK),
> (u64)sizeof(struct setup_data));
> data = early_memremap(pa_data, map_len);
> data_len = data->len + sizeof(struct setup_data);
> - if (data_len > map_len) {
> - early_iounmap(data, map_len);
> - data = early_memremap(pa_data, data_len);
> - map_len = data_len;
> - }
>
> switch (data->type) {
> case SETUP_E820_EXT:
> + remap_setup_data(pa_data, data_len, &data, &map_len);
> parse_e820_ext(data);
> break;
> case SETUP_DTB:

how about just passing phys_addr and length with parse_e820_ext and parse_dtb?
let them to worry about length and handle oversize case.

Thanks

Yinghai


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