PCI: rcar: Fix a potential NULL pointer dereference

[ Upstream commit f0d14edd2ba43b995bef4dd5da5ffe0ae19321a1 ]

In case __get_free_pages() fails and returns NULL, fix the return
value to -ENOMEM and release resources to avoid dereferencing a
NULL pointer.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/pci/controller/pcie-rcar.c

@@ -931,6 +931,10 @@ static int rcar_pcie_enable_msi(struct rcar_pcie *pcie)
 
 	/* setup MSI data target */
 	msi->pages = __get_free_pages(GFP_KERNEL, 0);
+	if (!msi->pages) {
+		err = -ENOMEM;
+		goto err;
+	}
 	base = virt_to_phys((void *)msi->pages);
 
 	rcar_pci_write_reg(pcie, base | MSIFE, PCIEMSIALR);