Re: [Xen-devel] [PATCH v2] PCI: Add guard to avoid mapping a invalid msix base address

[Bjorn Helgaas <bhelgaas@xxxxxxxxxx>]

[+cc Konrad, Boris, David, xen-devel, Alex, kvm]

On Wed, Jan 28, 2015 at 09:52:17AM +0800, Yijing Wang wrote:
> Sometimes, a pci bridge device BAR was not assigned
> properly. After we call pci_bus_assign_resources(), the
> resource of the BAR would be reseted. So if we try to
> enable msix for this device, it will map a invalid
> resource as the msix base address, and a warning call trace
> will report.
> 
> pci_bus_assign_resources()
>       __pci_bus_assign_resources()
>               pbus_assign_resources_sorted()
>                       __assign_resources_sorted()
>                               assign_requested_resources_sorted()
>                                       pci_assign_resource() -->fail
>                                       reset_resource()        
> -->res->start/end/flags = 0
> 
> pcie_port_device_register()
>       init_service_irqs()
>               pcie_port_enable_msix()
>                       ...
>                               msix_capability_init()
>                                       msix_map_region()
>                                               phys_addr = 
> pci_resource_start(dev, bir) + table_offset;
> If BAR(index=bir) was not assign properly, pci_resource_start(dev, bir)
> here would return 0, so phys_addr is a invalid physical
> address of msix.
> 
> [   43.094087] ------------[ cut here ]------------
> [   43.097418] WARNING: CPU: 1 PID: 1800 at arch/arm64/mm/ioremap.c:58 
> __ioremap_caller+0xd4/0xe8()
> ...
> [   43.121694] CPU: 1 PID: 1800 Comm: insmod Tainted: G           O  3.16.0 #5
> [   43.127374] Call trace:
> [   43.128522] [<ffffffc0000891d4>] dump_backtrace+0x0/0x130
> [   43.132637] [<ffffffc000089314>] show_stack+0x10/0x1c
> [   43.136402] [<ffffffc0004db040>] dump_stack+0x74/0x94
> [   43.140166] [<ffffffc0000986f8>] warn_slowpath_common+0x8c/0xb4
> [   43.144804] [<ffffffc0000987e4>] warn_slowpath_null+0x14/0x20
> [   43.149266] [<ffffffc000095474>] __ioremap_caller+0xd0/0xe8
> [   43.153555] [<ffffffc000095498>] __ioremap+0xc/0x18
> [   43.157145] [<ffffffc0002cc62c>] pci_enable_msix+0x238/0x44c
> [   43.161521] [<ffffffc0002cc874>] pci_enable_msix_range+0x34/0x80
> [   43.166243] [<ffffffc0002c946c>] pcie_port_device_register+0x104/0x480
> [   43.171491] [<ffffffc0002c99f8>] pcie_portdrv_probe+0x38/0xa0
> [   43.175952] [<ffffffc0002bd6c8>] pci_device_probe+0x78/0xd4
> [   43.180238] [<ffffffc00030e68c>] really_probe+0x6c/0x22c
> [   43.184265] [<ffffffc00030e8a8>] __device_attach+0x5c/0x6c
> [   43.188466] [<ffffffc00030cb68>] bus_for_each_drv+0x50/0x94
> [   43.192755] [<ffffffc00030e5fc>] device_attach+0x9c/0xc0
> [   43.196780] [<ffffffc0002b4c54>] pci_bus_add_device+0x38/0x80
> [   43.201243] [<ffffffc0002b5064>] pci_bus_add_devices+0x4c/0xd4
> [   43.205791] [<ffffffc000093d70>] pci_common_init+0x274/0x378
> [   43.210170] [<ffffffbff18e4b8c>] $x+0xb8c/0xc88 [pcie]
> [   43.214024] [<ffffffc00031013c>] platform_drv_probe+0x20/0x58
> [   43.218483] [<ffffffc00030e6e4>] really_probe+0xc4/0x22c
> [   43.222510] [<ffffffc00030e958>] __driver_attach+0xa0/0xa8
> [   43.226708] [<ffffffc00030cab0>] bus_for_each_dev+0x54/0x98
> [   43.231000] [<ffffffc00030e234>] driver_attach+0x1c/0x28
> [   43.235024] [<ffffffc00030deb0>] bus_add_driver+0x14c/0x204
> [   43.239309] [<ffffffc00030f038>] driver_register+0x64/0x130
> [   43.243598] [<ffffffc000310110>] __platform_driver_register+0x5c/0x68
> [   43.248757] [<ffffffc0003101b4>] platform_driver_probe+0x28/0xac
> [   43.253485] [<ffffffbff18e4cb8>] pcie_init+0x30/0x3c [pcie]
> [   43.258293] [<ffffffc0000815dc>] do_one_initcall+0x88/0x19c
> [   43.262585] [<ffffffc0000f6b74>] load_module+0xc2c/0xf2c
> [   43.266609] [<ffffffc0000f6fd0>] SyS_finit_module+0x78/0x88
> [   43.270897] ---[ end trace ea5eb60837afb5aa ]---
> 
> Reported-by: Zhang Jukuo<zhangjukuo@xxxxxxxxxx>
> Tested-by: Zhang Jukuo<zhangjukuo@xxxxxxxxxx>
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> ---
>  drivers/pci/msi.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index fd60806..c3e7dfc 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -694,11 +694,16 @@ static void __iomem *msix_map_region(struct pci_dev 
> *dev, unsigned nr_entries)
>  {
>       resource_size_t phys_addr;
>       u32 table_offset;
> +     unsigned long flags;
>       u8 bir;
>  
>       pci_read_config_dword(dev, dev->msix_cap + PCI_MSIX_TABLE,
>                             &table_offset);
>       bir = (u8)(table_offset & PCI_MSIX_TABLE_BIR);
> +     flags = pci_resource_flags(dev, bir);
> +     if (!flags || (flags & IORESOURCE_UNSET))
> +             return NULL;

Thanks, this looks better.

There's similar code in xen_initdom_setup_msi_irqs() that looks like it
might require a similar fix.

vfio_pci_enable() also looks at PCI_MSIX_TABLE_BIR, but I *think* it's safe
because it doesn't actually look at the memory space mapped by the BAR.

There would be a similar hazard with PCI_MSIX_PBA_BIR, but it looks like
nobody uses the Pending Bit Array at all, so I don't see an issue there.

>       table_offset &= PCI_MSIX_TABLE_OFFSET;
>       phys_addr = pci_resource_start(dev, bir) + table_offset;
>  
> -- 
> 1.7.1
> 
> --
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