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authorJoerg Roedel <jroedel@suse.de>2020-10-28 17:46:59 +0100
committerBorislav Petkov <bp@suse.de>2020-10-29 19:27:42 +0100
commit2411cd82112397bfb9d8f0f19cd46c3d71e0ce67 (patch)
treeb49db12b5fb9ca93bd04725ab135439b153b381f /arch
parentc9f09539e16e281f92a27760fdfae71e8af036f6 (diff)
downloadlinux-stericsson-2411cd82112397bfb9d8f0f19cd46c3d71e0ce67.tar.gz
x86/sev-es: Do not support MMIO to/from encrypted memory
MMIO memory is usually not mapped encrypted, so there is no reason to support emulated MMIO when it is mapped encrypted. Prevent a possible hypervisor attack where a RAM page is mapped as an MMIO page in the nested page-table, so that any guest access to it will trigger a #VC exception and leak the data on that page to the hypervisor via the GHCB (like with valid MMIO). On the read side this attack would allow the HV to inject data into the guest. Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com> Link: https://lkml.kernel.org/r/20201028164659.27002-6-joro@8bytes.org
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/sev-es.c20
1 files changed, 13 insertions, 7 deletions
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 4a96726fbaf8..0bd1a0fc587e 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -374,8 +374,8 @@ fault:
return ES_EXCEPTION;
}
-static bool vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
- unsigned long vaddr, phys_addr_t *paddr)
+static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
+ unsigned long vaddr, phys_addr_t *paddr)
{
unsigned long va = (unsigned long)vaddr;
unsigned int level;
@@ -394,15 +394,19 @@ static bool vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
if (user_mode(ctxt->regs))
ctxt->fi.error_code |= X86_PF_USER;
- return false;
+ return ES_EXCEPTION;
}
+ if (WARN_ON_ONCE(pte_val(*pte) & _PAGE_ENC))
+ /* Emulated MMIO to/from encrypted memory not supported */
+ return ES_UNSUPPORTED;
+
pa = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
pa |= va & ~page_level_mask(level);
*paddr = pa;
- return true;
+ return ES_OK;
}
/* Include code shared with pre-decompression boot stage */
@@ -731,6 +735,7 @@ static enum es_result vc_do_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
{
u64 exit_code, exit_info_1, exit_info_2;
unsigned long ghcb_pa = __pa(ghcb);
+ enum es_result res;
phys_addr_t paddr;
void __user *ref;
@@ -740,11 +745,12 @@ static enum es_result vc_do_mmio(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
exit_code = read ? SVM_VMGEXIT_MMIO_READ : SVM_VMGEXIT_MMIO_WRITE;
- if (!vc_slow_virt_to_phys(ghcb, ctxt, (unsigned long)ref, &paddr)) {
- if (!read)
+ res = vc_slow_virt_to_phys(ghcb, ctxt, (unsigned long)ref, &paddr);
+ if (res != ES_OK) {
+ if (res == ES_EXCEPTION && !read)
ctxt->fi.error_code |= X86_PF_WRITE;
- return ES_EXCEPTION;
+ return res;
}
exit_info_1 = paddr;