Hi,
On 9/1/22 13:34, Andy Shevchenko wrote:
> We have to copy only selected fields from the original resource.
> Because a PCI device will be removed immediately after getting
> its resources, we may not use any allocated data, hence we may
> not copy any pointers.
>
> Consider the following scenario:
>
> 1/ a caller of p2sb_bar() gets the resource;
>
> 2/ the resource has been copied by platform_device_add_data()
> in order to create a platform device;
>
> 3/ the platform device creation will call for the device driver's
> ->probe() as soon as a match found;
>
> 4/ the ->probe() takes given resources (see 2/) and tries to
> access one of its field, i.e. 'name', in the
> __devm_ioremap_resource() to create a pretty looking output;
>
> 5/ but the 'name' is a dangling pointer because p2sb_bar()
> removed a PCI device, which 'name' had been copied to
> the caller's memory.
>
> 6/ UAF (Use-After-Free) as a result.
>
> Kudos to Mika for the initial analisys of the issue.
>
> Fixes: 9745fb07474f ("platform/x86/intel: Add Primary to Sideband (P2SB) bridge support")
> Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> Suggested-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> Link: https://lore.kernel.org/linux-i2c/YvPCbnKqDiL2XEKp@xsang-OptiPlex-9020/
> Link: https://lore.kernel.org/linux-i2c/YtjAswDKfiuDfWYs@xsang-OptiPlex-9020/
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Thank you for your patch, I've applied this patch to my review-hans
branch:
https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=review-hans
Note it will show up in my review-hans branch once I've pushed my
local branch there, which might take a while.
Once I've run some tests on this branch the patches there will be
added to the platform-drivers-x86/for-next branch and eventually
will be included in the pdx86 pull-request to Linus for the next
merge-window.
Regards,
Hans
> ---
> drivers/platform/x86/p2sb.c | 18 ++++++++++++++++--
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/platform/x86/p2sb.c b/drivers/platform/x86/p2sb.c
> index fb2e141f3eb8..384d0962ae93 100644
> --- a/drivers/platform/x86/p2sb.c
> +++ b/drivers/platform/x86/p2sb.c
> @@ -42,10 +42,24 @@ static int p2sb_get_devfn(unsigned int *devfn)
> return 0;
> }
>
> +/* Copy resource from the first BAR of the device in question */
> static int p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem)
> {
> - /* Copy resource from the first BAR of the device in question */
> - *mem = pdev->resource[0];
> + struct resource *bar0 = &pdev->resource[0];
> +
> + /* Make sure we have no dangling pointers in the output */
> + memset(mem, 0, sizeof(*mem));
> +
> + /*
> + * We copy only selected fields from the original resource.
> + * Because a PCI device will be removed soon, we may not use
> + * any allocated data, hence we may not copy any pointers.
> + */
> + mem->start = bar0->start;
> + mem->end = bar0->end;
> + mem->flags = bar0->flags;
> + mem->desc = bar0->desc;
> +
> return 0;
> }
>
