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From: Greg KH <gregkh@linuxfoundation.org>
To: "Schmid, Carsten" <Carsten_Schmid@mentor.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
	Andrey Konovalov <andreyknvl@google.com>,
	Oliver Neukum <oneukum@suse.com>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	syzbot <syzbot+ef5de9c4f99c4edb4e49@syzkaller.appspotmail.com>,
	USB list <linux-usb@vger.kernel.org>,
	Hillf Danton <hdanton@sina.com>
Subject: Re: KASAN: use-after-free Read in usbhid_power
Date: Fri, 9 Aug 2019 09:55:55 +0200
Message-ID: <20190809075555.GA20409@kroah.com> (raw)
In-Reply-To: <caf422aebd314ab8a5dd96ac2d9bb198@SVR-IES-MBX-03.mgc.mentorg.com>

On Fri, Aug 09, 2019 at 07:35:32AM +0000, Schmid, Carsten wrote:
> Hi all having use-after-free issues in USB shutdowns:
> I hunted for a similar case in the intel_xhci_usb_sw driver.
> What i have found and proposed is (from yesterday):
> ---
> [PATCH] kernel/resource.c: invalidate parent when freed resource has childs
> 
> 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@mentor.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.
> ---
>  kernel/resource.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/kernel/resource.c b/kernel/resource.c
> index 158f04ec1d4f..95340cb0b1c2 100644
> --- 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);

Nit, should't this be written so that you only drop/get the lock if the
above if statement is true?

> +                       if (res->child) {
> +                               printk(KERN_WARNING "__release_region: %s has child %s,"
> +                                               "invalidating childs parent\n",
> +                                               res->name, res->child->name);

What can userspace/anyone do about this if it triggers?

Can't we fix the root problem in the xhci driver to properly order how
it tears things down?  If it has intel_xhci_usb_driver as a "child"
shouldn't that be unbound/freed before the parent is?

thanks,

greg k-h

  reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-23 12:48 syzbot
2019-07-24 14:17 ` Oliver Neukum
2019-07-24 14:24   ` Andrey Konovalov
2019-07-24 20:55 ` Oliver Neukum
2019-07-24 21:02   ` Alan Stern
2019-07-25  9:33     ` Oliver Neukum
2019-07-25 15:09       ` Alan Stern
2019-08-08 18:54         ` Andrey Konovalov
2019-08-08 19:37           ` Alan Stern
2019-08-09  7:35             ` AW: " Schmid, Carsten
2019-08-09  7:55               ` Greg KH [this message]
2019-08-09  9:34                 ` Schmid, Carsten
2019-08-09 10:20                   ` Hans de Goede
2019-08-09 10:47                     ` AW: " Schmid, Carsten
2019-08-09 10:53                       ` Hans de Goede
2019-08-09 12:38                         ` AW: " Schmid, Carsten
2019-08-09 12:54                           ` Greg KH
2019-08-09 13:00                             ` AW: " Schmid, Carsten
2019-08-09 13:38                               ` Greg KH
2019-08-10 11:12                           ` AW: " Hans de Goede
2019-08-09 17:36             ` Andrey Konovalov
2019-08-09 18:12               ` syzbot
2019-08-12 14:29                 ` Andrey Konovalov
2019-08-09 20:26           ` Oliver Neukum
2019-07-24 21:16   ` syzbot
2019-07-25 11:22     ` Andrey Konovalov
2019-07-25 12:15 ` Oliver Neukum
2019-07-25 12:27   ` syzbot

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