[Qemu-devel] [liqiang6-s@360.cn: 答复: Host memory leakage in QEMU xhci device emulation]

["Michael S. Tsirkin" <mst@redhat.com>]

----- Forwarded message from 李强 <liqiang6-s@360.cn> -----

Date: Fri, 22 Jul 2016 03:48:38 +0000
From: 李强 <liqiang6-s@360.cn>
To: "Michael S. Tsirkin" <mst@redhat.com>
Subject: 答复: Host memory leakage  in QEMU  xhci device emulation
Message-ID: <143C0AFC63FC204CB0C55BB88F3A8ABB0181D7F7@EX02.corp.qihoo.net>
In-Reply-To: <20160722063935-mutt-send-email-mst@kernel.org>

Right, a user can hotplug a lot of devices.
It is a bug not a security issue. Just publish it.

> -----邮件原件-----
> 发件人: Michael S. Tsirkin [mailto:mst@redhat.com]
> 发送时间: 2016年7月22日 11:42
> 收件人: 李强
> 抄送: pmatouse@redhat.com; sstabellini@kernel.org; secalert@redhat.com;
> mdroth@linux.vnet.ibm.com
> 主题: Re: Host memory leakage in QEMU xhci device emulation
> 
> On Fri, Jul 22, 2016 at 02:42:56AM +0000, 李强 wrote:
> > Hi,
> >
> >
> >
> > I found a host memory leakage issue in QEMU hcd-xhci device emulation.
> >
> >
> >
> > DESCRIPTION
> >
> > _____
> >
> >
> >
> > In usb_xhci_realize() function, it calls msix_init() which requires
> > memory malloc. In usb_xhci_exit(), it doesn't call the corresponding
> > function
> > msix_uninit() to free the memory.
> >
> > This will cause host memory leakage if a malicious hotplug and unplug
> > the xhci device.
> 
> Thanks for the resport.
> 
> I would say whoever can hotplug devices can just hotplug a hoge number of
> these until you run out of memory.
> So I don't think it's a security vulnerability, but we should fix it.
> 
> Do you agree? If yes we can publish this on the qemu mailing list.
> 
> 
> >
> >
> > code from hw/usb/hcd-xhci.c
> >
> > static void usb_xhci_realize(struct PCIDevice *dev, Error **errp)
> >
> > {
> >
> >     int i, ret;
> >
> >
> >
> >     if (xhci_get_flag(xhci, XHCI_FLAG_USE_MSI_X)) {
> >
> >         msix_init(dev, xhci->numintrs,
> >
> >                   &xhci->mem, 0, OFF_MSIX_TABLE,
> >
> >                   &xhci->mem, 0, OFF_MSIX_PBA,
> >
> >                   0x90);
> >
> >     }
> >
> > }
> >
> >
> >
> > static void usb_xhci_exit(PCIDevice *dev)
> >
> > {
> >
> >     int i;
> >
> >     XHCIState *xhci = XHCI(dev);
> >
> >
> >
> >     trace_usb_xhci_exit();
> >
> >
> >
> >     for (i = 0; i < xhci->numslots; i++) {
> >
> >         xhci_disable_slot(xhci, i + 1);
> >
> >     }
> >
> >
> >
> >     if (xhci->mfwrap_timer) {
> >
> >         timer_del(xhci->mfwrap_timer);
> >
> >         timer_free(xhci->mfwrap_timer);
> >
> >         xhci->mfwrap_timer = NULL;
> >
> >     }
> >
> >
> >
> >     /* destroy msix memory region *///here just destroy the memory
> > region, doesn’t free the msix memory
> >
> >     if (dev->msix_table && dev->msix_pba
> >
> >         && dev->msix_entry_used) {
> >
> >         memory_region_del_subregion(&xhci->mem,
> > &dev->msix_table_mmio);
> >
> >         memory_region_del_subregion(&xhci->mem,
> &dev->msix_pba_mmio);
> >
> >     }
> >
> >
> >
> >     usb_bus_release(&xhci->bus);
> >
> > }
> >
> >
> >
> > DEBUG AND TEST INFO
> >
> > _____
> >
> >
> >
> > Breakpoint 1, usb_xhci_realize (dev=0x5555592e7c20,
> > errp=0x7fffffffc5f8) at hw/
> > usb/hcd-xhci.c:3652
> >
> > 3652                 msix_init(dev, xhci->numintrs,
> >
> > (gdb) p dev->msix_table
> >
> > $1 = (uint8_t *) 0x0
> >
> > (gdb) p dev->msix_pba
> >
> > $2 = (uint8_t *) 0x0
> >
> > (gdb) p dev->msix_entry_used
> >
> > $3 = (unsigned int *) 0x0
> >
> > (gdb) n
> >
> > [Thread 0x7fffe72f7700 (LWP 49433) exited]
> >
> > 3657         }
> >
> > (gdb) p dev->msix_table
> >
> > $4 = (uint8_t *) 0x55555823a480 ""
> >
> > (gdb) p dev->msix_pba
> >
> > $5 = (uint8_t *) 0x55555823a590 ""
> >
> > (gdb) p dev->msix_entry_used
> >
> > $6 = (unsigned int *) 0x55555823a5b0
> >
> > (gdb) c
> >
> > Continuing.
> >
> >
> >
> > Program received signal SIGPIPE, Broken pipe.
> >
> > 0x00007ffff69ed78d in sendmsg () at
> > ../sysdeps/unix/syscall-template.S:81
> >
> > 81     T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
> >
> > (gdb) i b
> >
> > Num     Type           Disp Enb Address            What
> >
> > 1       breakpoint     keep y   0x00005555559c6a68 in
> usb_xhci_realize at hw/
> > usb/hcd-xhci.c:3652
> >
> >          breakpoint already hit 1 time
> >
> > 2       breakpoint     keep y   0x00005555559c6c5e in usb_xhci_exit
> at hw/usb/
> > hcd-xhci.c:3686
> >
> > (gdb) d 1
> >
> > (gdb) c
> >
> > Continuing.
> >
> > [New Thread 0x7fffe72f7700 (LWP 49451)]
> >
> > [Switching to Thread 0x7fffe5a04700 (LWP 49408)]
> >
> >
> >
> > Breakpoint 2, usb_xhci_exit (dev=0x5555592e7c20) at
> > hw/usb/hcd-xhci.c:3687
> >
> > 3687             if (dev->msix_table && dev->msix_pba
> >
> > (gdb) p dev->msix_table
> >
> > $7 = (uint8_t *) 0x55555823a480 "\f\020\340\376"
> >
> > (gdb) p dev->msix_pba
> >
> > $8 = (uint8_t *) 0x55555823a590 ""
> >
> > (gdb) p dev->msix_entry_used
> >
> > $9 = (unsigned int *) 0x55555823a5b0
> >
> > (gdb) n
> >
> > 3688                 && dev->msix_entry_used) {
> >
> > (gdb) n
> >
> > 3689                 memory_region_del_subregion(&xhci->mem,
> &dev->
> > msix_table_mmio);
> >
> > (gdb) awatch *(int*)0x55555823a480              // this three
> breakpoint never
> > triggered
> >
> > Hardware access (read/write) watchpoint 3: *(int*)0x55555823a480
> >
> > (gdb) awatch *(int*)0x55555823a590
> >
> > Hardware access (read/write) watchpoint 4: *(int*)0x55555823a590
> >
> > (gdb) awatch *(int*)0x55555823a5b0
> >
> > Hardware access (read/write) watchpoint 5: *(int*)0x55555823a5b0
> >
> > (gdb) c
> >
> > Continuing.
> >
> > [Thread 0x7fffe72f7700 (LWP 49451) exited]
> >
> > [New Thread 0x7fffe72f7700 (LWP 49468)]
> >
> >
> >
> >
> >
> > I use a script modified from https://gist.github.com/sibiaoluo/9798832
> > to send qmp commands.
> >
> > The script is in attachment. We can see the memory usage is raising.
> >
> >
> >
> >    PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM
> TIME+
> > COMMAND
> >
> >  48833 root      20   0 2735700 2.057g   5152 R 149.0 70.3  34:42.56
> > qemu-system-x86
> >
> >
> >
> > REPRODUCE
> >
> > _____
> >
> >
> >
> > command used:gdb --args ./qemu-system-x86_64 -m 2048 -hda
> > /root/centos6.img -enable-kvm -qmp unix:/tmp/qmp-socket,server,nowait
> >
> >
> >
> > Then run the attachment script, it will show the qemu process memory
> > usage is raising.
> >
> >
> >
> > TEST ENVIRONMENT
> >
> > _____
> >
> >
> >
> > CentOS 7 x64
> >
> > http://wiki.qemu-project.org/download/qemu-2.6.0.tar.bz2
> >
> >
> >
> > Thanks,
> >
> >
> >
> > Li Qiang of the Cloud Security Team, Qihoo 360 Inc.
> >
> 


----- End forwarded message -----