From: Brijesh Singh Date: Wed, 9 Feb 2022 18:10:14 +0000 (-0600) Subject: x86/kernel: Validate ROM memory before accessing when SEV-SNP is active X-Git-Tag: v6.1-rc5~1348^2~40 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=9704c07bf9f7682a83aec4e66f2d9154dbd8577f;p=platform%2Fkernel%2Flinux-starfive.git x86/kernel: Validate ROM memory before accessing when SEV-SNP is active probe_roms() accesses the memory range (0xc0000 - 0x10000) to probe various ROMs. The memory range is not part of the E820 system RAM range. The memory range is mapped as private (i.e encrypted) in the page table. When SEV-SNP is active, all the private memory must be validated before accessing. The ROM range was not part of E820 map, so the guest BIOS did not validate it. An access to invalidated memory will cause a exception yet, so validate the ROM memory regions before it is accessed. [ bp: Massage commit message. ] Signed-off-by: Brijesh Singh Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220307213356.2797205-21-brijesh.singh@amd.com --- diff --git a/arch/x86/kernel/probe_roms.c b/arch/x86/kernel/probe_roms.c index 36e84d9..319fef3 100644 --- a/arch/x86/kernel/probe_roms.c +++ b/arch/x86/kernel/probe_roms.c @@ -21,6 +21,7 @@ #include #include #include +#include static struct resource system_rom_resource = { .name = "System ROM", @@ -197,11 +198,21 @@ static int __init romchecksum(const unsigned char *rom, unsigned long length) void __init probe_roms(void) { - const unsigned char *rom; unsigned long start, length, upper; + const unsigned char *rom; unsigned char c; int i; + /* + * The ROM memory range is not part of the e820 table and is therefore not + * pre-validated by BIOS. The kernel page table maps the ROM region as encrypted + * memory, and SNP requires encrypted memory to be validated before access. + * Do that here. + */ + snp_prep_memory(video_rom_resource.start, + ((system_rom_resource.end + 1) - video_rom_resource.start), + SNP_PAGE_STATE_PRIVATE); + /* video rom */ upper = adapter_rom_resources[0].start; for (start = video_rom_resource.start; start < upper; start += 2048) {