linux-kernel - [PATCH 4.19 54/84] PCI: dwc: Fix find_next

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Date:   Fri, 17 Jan 2020 00:18:28 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Niklas Cassel <niklas.cassel@...aro.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <andrew.murray@....com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>
Subject: [PATCH 4.19 54/84] PCI: dwc: Fix find_next_bit() usage

From: Niklas Cassel <niklas.cassel@...aro.org>

commit 1137e61dcb99f7f8b54e77ed83f68b5b485a3e34 upstream.

find_next_bit() takes a parameter of size long, and performs arithmetic
that assumes that the argument is of size long.

Therefore we cannot pass a u32, since this will cause find_next_bit()
to read outside the stack buffer and will produce the following print:
BUG: KASAN: stack-out-of-bounds in find_next_bit+0x38/0xb0

Fixes: 1b497e6493c4 ("PCI: dwc: Fix uninitialized variable in dw_handle_msi_irq()")
Tested-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Signed-off-by: Niklas Cassel <niklas.cassel@...aro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Reviewed-by: Andrew Murray <andrew.murray@....com>
Acked-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/pci/controller/dwc/pcie-designware-host.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -78,7 +78,8 @@ static struct msi_domain_info dw_pcie_ms
 irqreturn_t dw_handle_msi_irq(struct pcie_port *pp)
 {
 	int i, pos, irq;
-	u32 val, num_ctrls;
+	unsigned long val;
+	u32 status, num_ctrls;
 	irqreturn_t ret = IRQ_NONE;
 
 	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
@@ -86,14 +87,14 @@ irqreturn_t dw_handle_msi_irq(struct pci
 	for (i = 0; i < num_ctrls; i++) {
 		dw_pcie_rd_own_conf(pp, PCIE_MSI_INTR0_STATUS +
 					(i * MSI_REG_CTRL_BLOCK_SIZE),
-				    4, &val);
-		if (!val)
+				    4, &status);
+		if (!status)
 			continue;
 
 		ret = IRQ_HANDLED;
+		val = status;
 		pos = 0;
-		while ((pos = find_next_bit((unsigned long *) &val,
-					    MAX_MSI_IRQS_PER_CTRL,
+		while ((pos = find_next_bit(&val, MAX_MSI_IRQS_PER_CTRL,
 					    pos)) != MAX_MSI_IRQS_PER_CTRL) {
 			irq = irq_find_mapping(pp->irq_domain,
 					       (i * MAX_MSI_IRQS_PER_CTRL) +