[PATCH] ACPI/PPTT: fix off-by-one error

Heyne, Maximilian
2025-05-06T13:13:08Z

Commit 7ab4f0e37a0f ("ACPI PPTT: Fix coding mistakes in a couple of
sizeof() calls") corrects the processer entry size but unmasked a longer
standing bug where the last entry in the structure can get skipped due
to an off-by-one mistake if the last entry ends exactly at the end of
the ACPI subtable.

The error manifests for instance on EC2 Graviton Metal instances with

ACPI PPTT: PPTT table found, but unable to locate core 63 (63)
[...]
ACPI: SPE must be homogeneous

Fixes: 2bd00bcd73e5 ("ACPI/PPTT: Add Processor Properties Topology Table parsing")
Cc: stable@vger.kernel.org
Signed-off-by: Maximilian Heyne <mheyne@amazon.de>
---
drivers/acpi/pptt.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index f73ce6e13065d..4364da90902e5 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -231,7 +231,7 @@ static int acpi_pptt_leaf_node(struct acpi_table_header *table_hdr,
sizeof(struct acpi_table_pptt));
proc_sz = sizeof(struct acpi_pptt_processor);

- while ((unsigned long)entry + proc_sz < table_end) {
+ while ((unsigned long)entry + proc_sz <= table_end) {
cpu_node = (struct acpi_pptt_processor *)entry;
if (entry->type == ACPI_PPTT_TYPE_PROCESSOR &&
cpu_node->parent == node_entry)
@@ -273,7 +273,7 @@ static struct acpi_pptt_processor *acpi_find_processor_node(struct acpi_table_he
proc_sz = sizeof(struct acpi_pptt_processor);

/* find the processor structure associated with this cpuid */
- while ((unsigned long)entry + proc_sz < table_end) {
+ while ((unsigned long)entry + proc_sz <= table_end) {
cpu_node = (struct acpi_pptt_processor *)entry;

if (entry->length == 0) {
--
2.47.1

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