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SubjectRe: [PATCH] PCI: dwc: fix find_next_bit() usage
On Wed, Sep 4, 2019 at 9:03 AM Niklas Cassel <niklas.cassel@linaro.org> wrote:
>
> 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()")
> Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>

Tested-by: Bjorn Andersson <bjorn.andersson@linaro.org>

> ---
> drivers/pci/controller/dwc/pcie-designware-host.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index d3156446ff27..45f21640c977 100644
> --- 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_msi_domain_info = {
> 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 pcie_port *pp)
> 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) +
> --
> 2.21.0
>

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