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SubjectRe: [PATCH] switchtec: Fix potential Spectre v1
On Thu, Aug 16, 2018 at 02:06:46PM -0500, Gustavo A. R. Silva wrote:
> p.port can is indirectly controlled by user-space, hence leading to
> a potential exploitation of the Spectre variant 1 vulnerability.
>
> This issue was detected with the help of Smatch:
>
> drivers/pci/switch/switchtec.c:912 ioctl_port_to_pff() warn: potential
> spectre issue 'pcfg->dsp_pff_inst_id' [r]
>
> Fix this by sanitizing p.port before using it to index
> pcfg->dsp_pff_inst_id
>
> Notice that given that speculation windows are large, the policy is
> to kill the speculation on the first load and not worry if it can be
> completed with a dependent load/store [1].
>
> [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>

Applied with Logan's ack to for-linus for v4.19, thanks!

> ---
> drivers/pci/switch/switchtec.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c
> index 9940cc7..54a8b30 100644
> --- a/drivers/pci/switch/switchtec.c
> +++ b/drivers/pci/switch/switchtec.c
> @@ -14,6 +14,8 @@
> #include <linux/poll.h>
> #include <linux/wait.h>
>
> +#include <linux/nospec.h>
> +
> MODULE_DESCRIPTION("Microsemi Switchtec(tm) PCIe Management Driver");
> MODULE_VERSION("0.1");
> MODULE_LICENSE("GPL");
> @@ -909,6 +911,8 @@ static int ioctl_port_to_pff(struct switchtec_dev *stdev,
> default:
> if (p.port > ARRAY_SIZE(pcfg->dsp_pff_inst_id))
> return -EINVAL;
> + p.port = array_index_nospec(p.port,
> + ARRAY_SIZE(pcfg->dsp_pff_inst_id) + 1);
> p.pff = ioread32(&pcfg->dsp_pff_inst_id[p.port - 1]);
> break;
> }
> --
> 2.7.4
>

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