Re: [PATCH v5 18/32] x86, mpparse: Use memremap to map the mpf and mpc data

Borislav Petkov
2017-05-16T08:37:13Z

On Tue, Apr 18, 2017 at 04:19:30PM -0500, Tom Lendacky wrote:
> The SMP MP-table is built by UEFI and placed in memory in a decrypted
> state. These tables are accessed using a mix of early_memremap(),
> early_memunmap(), phys_to_virt() and virt_to_phys(). Change all accesses
> to use early_memremap()/early_memunmap(). This allows for proper setting
> of the encryption mask so that the data can be successfully accessed when
> SME is active.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> arch/x86/kernel/mpparse.c | 102 +++++++++++++++++++++++++++++++--------------
> 1 file changed, 71 insertions(+), 31 deletions(-)
>
> diff --git a/arch/x86/kernel/mpparse.c b/arch/x86/kernel/mpparse.c
> index fd37f39..afbda41d 100644
> --- a/arch/x86/kernel/mpparse.c
> +++ b/arch/x86/kernel/mpparse.c
> @@ -429,7 +429,21 @@ static inline void __init construct_default_ISA_mptable(int mpc_default_type)
> }
> }
>
> -static struct mpf_intel *mpf_found;
> +static unsigned long mpf_base;
> +
> +static void __init unmap_mpf(struct mpf_intel *mpf)
> +{
> + early_memunmap(mpf, sizeof(*mpf));
> +}
> +
> +static struct mpf_intel * __init map_mpf(unsigned long paddr)
> +{
> + struct mpf_intel *mpf;
> +
> + mpf = early_memremap(paddr, sizeof(*mpf));
> +
> + return mpf;

return early_memremap(paddr, sizeof(*mpf));

...

> @@ -842,25 +873,26 @@ static int __init update_mp_table(void)
> if (!enable_update_mptable)
> return 0;
>
> - mpf = mpf_found;
> - if (!mpf)
> + if (!mpf_base)
> return 0;
>
> + mpf = map_mpf(mpf_base);
> +
> /*
> * Now see if we need to go further.
> */
> if (mpf->feature1 != 0)

You're kidding, right? map_mpf() *can* return NULL.

Also, simplify that test:

if (mpf->feature1)
...

> - return 0;
> + goto do_unmap_mpf;
>
> if (!mpf->physptr)
> - return 0;
> + goto do_unmap_mpf;
>
> - mpc = phys_to_virt(mpf->physptr);
> + mpc = map_mpc(mpf->physptr);

Again: error checking !!!

You have other calls to early_memremap()/map_mpf() in this patch. Please
add error checking everywhere.

>
> if (!smp_check_mpc(mpc, oem, str))
> - return 0;
> + goto do_unmap_mpc;
>
> - pr_info("mpf: %llx\n", (u64)virt_to_phys(mpf));
> + pr_info("mpf: %llx\n", (u64)mpf_base);
> pr_info("physptr: %x\n", mpf->physptr);
>
> if (mpc_new_phys && mpc->length > mpc_new_length) {
> @@ -878,21 +910,23 @@ static int __init update_mp_table(void)
> new = mpf_checksum((unsigned char *)mpc, mpc->length);
> if (old == new) {
> pr_info("mpc is readonly, please try alloc_mptable instead\n");
> - return 0;
> + goto do_unmap_mpc;
> }
> pr_info("use in-position replacing\n");
> } else {
> mpf->physptr = mpc_new_phys;
> - mpc_new = phys_to_virt(mpc_new_phys);
> + mpc_new = map_mpc(mpc_new_phys);

Ditto.

> memcpy(mpc_new, mpc, mpc->length);
> + unmap_mpc(mpc);
> mpc = mpc_new;
> /* check if we can modify that */
> if (mpc_new_phys - mpf->physptr) {
> struct mpf_intel *mpf_new;
> /* steal 16 bytes from [0, 1k) */
> pr_info("mpf new: %x\n", 0x400 - 16);
> - mpf_new = phys_to_virt(0x400 - 16);
> + mpf_new = map_mpf(0x400 - 16);

Ditto.

> memcpy(mpf_new, mpf, 16);
> + unmap_mpf(mpf);
> mpf = mpf_new;
> mpf->physptr = mpc_new_phys;
> }

--
Regards/Gruss,
Boris.

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