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acrn-hypervisor
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dm: mitigate reset attack 

When a platform reboots or shuts down, the contents of RAM are not immediately
lost but begins to decay. During this period, there is a short timeframe during
which an attacker can turn the platform back on to boot into a program that
dumps the contents of memory (e.g., cold boot attacks). Encryption keys and
other secrets can be easily compromised through this method.

We already erasing the guest memory data when the guest is shut down normally.
However, if the guest is shut down abnormally, the contents of RAM may still
there. This patch mitigate this kind reset attack for a DM launched VM by
erasing the guest memory data by the guest has been created.

Tracked-On: #6061
Signed-off-by: Li Fei1 <fei1.li@intel.com>
This commit is contained in:
Li Fei1 2021-05-24 11:25:50 +08:00 committed by wenlingz
parent 03fca4463c
commit 8ef2eedba4
1 changed files with 10 additions and 5 deletions
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15
devicemodel/core/vmmapi.c
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@ -376,6 +376,8 @@ vm_map_memseg_vma(struct vmctx *ctx, size_t len, vm_paddr_t gpa,
int int
vm_setup_memory(struct vmctx *ctx, size_t memsize) vm_setup_memory(struct vmctx *ctx, size_t memsize)
{ {
int ret;
/* /*
* If 'memsize' cannot fit entirely in the 'lowmem' segment then * If 'memsize' cannot fit entirely in the 'lowmem' segment then
* create another 'highmem' segment above 4GB for the remainder. * create another 'highmem' segment above 4GB for the remainder.
@ -390,7 +392,13 @@ vm_setup_memory(struct vmctx *ctx, size_t memsize)
ctx->biosmem = high_bios_size(); ctx->biosmem = high_bios_size();
return hugetlb_setup_memory(ctx); ret = hugetlb_setup_memory(ctx);
if (ret == 0) {
/* mitigate reset attack */
bzero((void *)ctx->baseaddr, ctx->lowmem);
bzero((void *)(ctx->baseaddr + ctx->highmem_gpa_base), ctx->highmem);
}
return ret;
} }
void void
@ -411,10 +419,7 @@ vm_unsetup_memory(struct vmctx *ctx)
if (!is_rtvm) { if (!is_rtvm) {
bzero((void *)ctx->baseaddr, ctx->lowmem); bzero((void *)ctx->baseaddr, ctx->lowmem);
if (ctx->highmem > 0) { bzero((void *)(ctx->baseaddr + ctx->highmem_gpa_base), ctx->highmem);
bzero((void *)(ctx->baseaddr + ctx->highmem_gpa_base),
ctx->highmem);
}
} }
hugetlb_unsetup_memory(ctx); hugetlb_unsetup_memory(ctx);