[PATCH] cxl/edac: Bounds-check ECS threshold index from device

[Yili Zhang <zhangyili01@baidu.com>]

cxl_get_ecs_threshold() extracts a 3-bit index (0-7) from the
device-supplied ECS config word and uses it to
index ecs_supp_threshold[], which only has 6 elements. A device reporting
index 6 or 7 causes an out-of-bounds read of adjacent .rodata, whose
value is then returned to userspace via the EDAC 'threshold' sysfs
attribute (small info leak and wrong reported threshold).

Return 0 for indices outside the table.

Fixes: 85fb6a16ad14 ("cxl/edac: Add CXL memory device ECS control feature")
Signed-off-by: Yili Zhang <zhangyili01@baidu.com>
---
 drivers/cxl/core/edac.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/cxl/core/edac.c b/drivers/cxl/core/edac.c
index b321971fef58..73335b980b11 100644
--- a/drivers/cxl/core/edac.c
+++ b/drivers/cxl/core/edac.c
@@ -633,6 +633,9 @@ static u16 cxl_get_ecs_threshold(u8 log_cap, u16 config)
 {
 	u8 index = FIELD_GET(CXL_ECS_THRESHOLD_COUNT_MASK, config);
 
+	if (index >= ARRAY_SIZE(ecs_supp_threshold))
+		return 0;
+
 	return ecs_supp_threshold[index];
 }
 
-- 
2.27.0