[PATCH] ARM64/ACPI: Fix BAD_MADT_GICC_ENTRY() macro implementation

[Lorenzo Pieralisi]

The BAD_MADT_GICC_ENTRY() macro checks if a GICC MADT entry passes
muster from an ACPI specification standpoint. Current macro detects the
MADT GICC entry length through ACPI firmware version (it changed from 76
to 80 bytes in the transition from ACPI 5.1 to ACPI 6.0 specification)
but always uses (erroneously) the ACPICA (latest) struct (ie struct
acpi_madt_generic_interrupt - that is 80-bytes long) length to check if
the current GICC entry memory record exceeds the MADT table end in
memory as defined by the MADT table header itself, which may result in
false negatives depending on the ACPI firmware version and how the MADT
entries are laid out in memory (ie on ACPI 5.1 firmware MADT GICC
entries are 76 bytes long, so by adding 80 to a GICC entry start address
in memory the resulting address may well be past the actual MADT end,
triggering a false negative).

Fix the BAD_MADT_GICC_ENTRY() macro by reshuffling the condition checks
and update them to always use the firmware version specific MADT GICC
entry length in order to carry out boundary checks.

Fixes: b6cfb277378e ("ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro")
Reported-by: Julien Grall <julien.grall at arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: Julien Grall <julien.grall at arm.com>
Cc: Hanjun Guo <hanjun.guo at linaro.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Al Stone <ahs3 at redhat.com>
Cc: Marc Zyngier <marc.zyngier at arm.com>
---
 arch/arm64/include/asm/acpi.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
index 0e99978..59cca1d 100644
--- a/arch/arm64/include/asm/acpi.h
+++ b/arch/arm64/include/asm/acpi.h
@@ -23,9 +23,9 @@
 #define ACPI_MADT_GICC_LENGTH	\
 	(acpi_gbl_FADT.header.revision < 6 ? 76 : 80)
 
-#define BAD_MADT_GICC_ENTRY(entry, end)						\
-	(!(entry) || (unsigned long)(entry) + sizeof(*(entry)) > (end) ||	\
-	 (entry)->header.length != ACPI_MADT_GICC_LENGTH)
+#define BAD_MADT_GICC_ENTRY(entry, end)					\
+	(!(entry) || (entry)->header.length != ACPI_MADT_GICC_LENGTH ||	\
+	(unsigned long)(entry) + ACPI_MADT_GICC_LENGTH > (end))
 
 /* Basic configuration for ACPI */
 #ifdef	CONFIG_ACPI
-- 
2.10.0