[PATCH 6.19 261/844] PCI: cadence: Avoid signed 64-bit truncation and invalid sort

[Sasha Levin]

From: Ian Rogers <irogers@xxxxxxxxxx>

[ Upstream commit 0297dce758a021ccf2c0f4e164d5403ef722961c ]

The cdns_pcie_host_dma_ranges_cmp() element comparison function used by
list_sort() is of type list_cmp_func_t, so it returns a 32-bit int.

cdns_pcie_host_dma_ranges_cmp() computes a resource_size_t difference that
may be a 64-bit value, and truncating that difference to a 32-bit return
value may change the sign and result in an invalid sort order.

Avoid the truncation and invalid sort order by returning -1, 0, or 1.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
Signed-off-by: Manivannan Sadhasivam <mani@xxxxxxxxxx>
[bhelgaas: commit log]
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Link: https://patch.msgid.link/20251209223756.2321578-1-irogers@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 .../controller/cadence/pcie-cadence-host-common.c    | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/cadence/pcie-cadence-host-common.c b/drivers/pci/controller/cadence/pcie-cadence-host-common.c
index 15415d7f35ee9..2b0211870f02a 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-host-common.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-host-common.c
@@ -173,11 +173,21 @@ int cdns_pcie_host_dma_ranges_cmp(void *priv, const struct list_head *a,
 				  const struct list_head *b)
 {
 	struct resource_entry *entry1, *entry2;
+	u64 size1, size2;
 
 	entry1 = container_of(a, struct resource_entry, node);
 	entry2 = container_of(b, struct resource_entry, node);
 
-	return resource_size(entry2->res) - resource_size(entry1->res);
+	size1 = resource_size(entry1->res);
+	size2 = resource_size(entry2->res);
+
+	if (size1 > size2)
+		return -1;
+
+	if (size1 < size2)
+		return 1;
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(cdns_pcie_host_dma_ranges_cmp);
 
-- 
2.51.0