[PATCH v2] cxl/region: Validate partition index before array access

[KobaK <kobak@nvidia.com>]

From: Koba Ko <kobak@nvidia.com>

construct_region() reads cxled->part and uses it to index
cxlds->part[] without checking for a negative value. If the
partition was never resolved, part remains at its initial value
of -1, causing an out-of-bounds array access.

Add a guard to return -EBUSY when part is negative.

Fixes: be5cbd084027 ("cxl: Kill enum cxl_decoder_mode")
Signed-off-by: Koba Ko <kobak@nvidia.com>
---
 drivers/cxl/core/region.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index edc267c6cf77..de749b54fd62 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3712,6 +3712,9 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
 	int rc, part = READ_ONCE(cxled->part);
 	struct cxl_region *cxlr;
 
+	if (part < 0)
+		return ERR_PTR(-EBUSY);
+
 	do {
 		cxlr = __create_region(cxlrd, cxlds->part[part].mode,
 				       atomic_read(&cxlrd->region_id),
-- 
2.43.0