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[PATCH 1/2] acpi/crs: Prevent bad ranges for host bridges

From: Ben Widawsky
Subject: [PATCH 1/2] acpi/crs: Prevent bad ranges for host bridges
Date: Mon, 26 Oct 2020 12:39:23 -0700

Prevent _CRS resources being quietly chopped off and instead throw an
assertion. _CRS is used by host bridges to declare regions of io and/or
memory that they consume. On some (all?) platforms the host bridge
doesn't have PCI header space and so they need some way to convey the

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>


1. I'm not aware of this being a real issue on platforms today as I think
   many platforms that use ACPI and actually have regions, constrain to
   32b to be complaint with legacy.
2. Since host bridges aren't usually hot plugged, it can't be invoked by
   a user, so assert() seems like the right way to handle this.
 hw/i386/acpi-build.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index eee7b57c37..df13abecf4 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -869,6 +869,8 @@ static Aml *build_crs(PCIHostState *host, CrsRangeSet 
     for (i = 0; i < temp_range_set.mem_ranges->len; i++) {
         entry = g_ptr_array_index(temp_range_set.mem_ranges, i);
+        assert(entry->limit <= UINT32_MAX &&
+               (entry->limit - entry->base + 1) <= UINT32_MAX);
                    aml_dword_memory(AML_POS_DECODE, AML_MIN_FIXED,
                                     AML_MAX_FIXED, AML_NON_CACHEABLE,

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