linux-kernel - [PATCH v2] PCI: Check value of resource alignment before using _

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Date:   Thu, 22 Apr 2021 16:25:38 +0530
From:   Amey Narkhede <ameynarkhede03@...il.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Leon Romanovsky <leon@...nel.org>,
        Amey Narkhede <ameynarkhede03@...il.com>
Subject: [PATCH v2] PCI: Check value of resource alignment before using __ffs

Return value of __ffs is undefined if no set bit exists in
its argument. This indicates that the associated BAR has
invalid alignment.

Signed-off-by: Amey Narkhede <ameynarkhede03@...il.com>
---
 drivers/pci/setup-bus.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 2ce636937c6e..ce5380bdd2fd 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1044,10 +1044,11 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
 			 * resources.
 			 */
 			align = pci_resource_alignment(dev, r);
-			order = __ffs(align) - 20;
-			if (order < 0)
-				order = 0;
-			if (order >= ARRAY_SIZE(aligns)) {
+			if (align) {
+				order = __ffs(align) - 20;
+				order = (order < 0) ? 0 : order;
+			}
+			if (!align || order >= ARRAY_SIZE(aligns)) {
 				pci_warn(dev, "disabling BAR %d: %pR (bad alignment %#llx)\n",
 					 i, r, (unsigned long long) align);
 				r->flags = 0;
--
2.31.1