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Message-ID: <2e93e4057d1f95680bdd6f7f7d754800b7c87ac9.camel@perches.com>
Date: Fri, 09 Aug 2019 11:37:31 -0700
From: Joe Perches <joe@...ches.com>
To: "Schmid, Carsten" <Carsten_Schmid@...tor.com>,
"bp@...e.de" <bp@...e.de>,
"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
"mingo@...nel.org" <mingo@...nel.org>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
"osalvador@...e.de" <osalvador@...e.de>,
"rdunlap@...radead.org" <rdunlap@...radead.org>,
"richardw.yang@...ux.intel.com" <richardw.yang@...ux.intel.com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>
Subject: Re: Resend [PATCH] kernel/resource.c: invalidate parent when freed
resource has childs
On Fri, 2019-08-09 at 13:50 +0000, Schmid, Carsten wrote:
> When a resource is freed and has children, the childrens are
> left without any hint that their parent is no more valid.
> This caused at least one use-after-free in the xhci-hcd using
> ext-caps driver when platform code released platform devices.
>
> Fix this by setting child's parent to zero and warn.
>
> Signed-off-by: Carsten Schmid <carsten_schmid@...tor.com>
> ---
> Rationale:
> When hunting for the root cause of a crash on a 4.14.86 kernel, i
> have found the root cause and checked it being still present
> upstream. Our case:
> Having xhci-hcd and intel_xhci_usb_sw active we can see in
> /proc/meminfo: (exceirpt)
> b3c00000-b3c0ffff : 0000:00:15.0
> b3c00000-b3c0ffff : xhci-hcd
> b3c08070-b3c0846f : intel_xhci_usb_sw
> intel_xhci_usb_sw being a child of xhci-hcd.
>
> Doing an unbind command
> echo 0000:00:15.0 > /sys/bus/pci/drivers/xhci_hcd/unbind
> leads to xhci-hcd being freed in __release_region.
> The intel_xhci_usb_sw resource is accessed in platform code
> in platform_device_del with
> for (i = 0; i < pdev->num_resources; i++) {
> struct resource *r = &pdev->resource[i];
> if (r->parent)
> release_resource(r);
> }
> as the resource's parent has not been updated, the release_resource
> uses the parent:
> p = &old->parent->child;
> which is now invalid.
> Fix this by marking the parent invalid in the child and give a warning
> in dmesg.
> ---
> Advised by Greg (thanks):
> Try resending it with at least the people who get_maintainer.pl says has
> touched that file last in it. [CS:done]
>
> Also, Linus is the unofficial resource.c maintainer. I think he has a
> set of userspace testing scripts for changes somewhere, so you should
> cc: him too. And might as well add me :) [CS:done]
[]
> diff --git a/kernel/resource.c b/kernel/resource.c
[]
> @@ -1200,6 +1200,15 @@ void __release_region(struct resource *parent, resource_size_t start,
> write_unlock(&resource_lock);
> if (res->flags & IORESOURCE_MUXED)
> wake_up(&muxed_resource_wait);
> +
> + write_lock(&resource_lock);
> + if (res->child) {
> + printk(KERN_WARNING "__release_region: %s has child %s,"
> + "invalidating childs parent\n",
> + res->name, res->child->name);
Please coalesce the format because there is likely an unintentional
missing space after the comma, and use pr_warn, %s and __func__
pr_warn("%s: %s has child %s, invalidating child's parent\n",
__func__, res->name, res->child->name);
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