[PATCH] powerpc/iommu: Fix notifiers being shared by PCI and VIO buses

[Andrew Donnellan]

On Wed, 2023-03-22 at 14:53 +1100, Russell Currey wrote:
> fail_iommu_setup() registers the fail_iommu_bus_notifier struct to
> both
> PCI and VIO buses.  struct notifier_block is a linked list node, so
> this
> causes any notifiers later registered to either bus type to also be
> registered to the other since they share the same node.
> 
> This causes issues in (at least) the vgaarb code, which registers a
> notifier for PCI buses.  pci_notify() ends up being called on a vio
> device, converted with to_pci_dev() even though it's not a PCI
> device,
> and finally makes a bad access in vga_arbiter_add_pci_device() as
> discovered with KASAN:
> 
>  BUG: KASAN: slab-out-of-bounds in
> vga_arbiter_add_pci_device+0x60/0xe00
>  Read of size 4 at addr c000000264c26fdc by task swapper/0/1
> 
>  Call Trace:
>  [c000000263607520] [c000000010f7023c] dump_stack_lvl+0x1bc/0x2b8
> (unreliable)
>  [c000000263607560] [c00000000f142a64] print_report+0x3f4/0xc60
>  [c000000263607640] [c00000000f142144] kasan_report+0x244/0x698
>  [c000000263607740] [c00000000f1460e8] __asan_load4+0xe8/0x250
>  [c000000263607760] [c00000000ff4b850]
> vga_arbiter_add_pci_device+0x60/0xe00
>  [c000000263607850] [c00000000ff4c678] pci_notify+0x88/0x444
>  [c0000002636078b0] [c00000000e94dfc4]
> notifier_call_chain+0x104/0x320
>  [c000000263607950] [c00000000e94f050]
> blocking_notifier_call_chain+0xa0/0x140
>  [c000000263607990] [c0000000100cb3b8] device_add+0xac8/0x1d30
>  [c000000263607aa0] [c0000000100ccd98] device_register+0x58/0x80
>  [c000000263607ad0] [c00000000e84247c]
> vio_register_device_node+0x9ac/0xce0
>  [c000000263607ba0] [c0000000126c95d8]
> vio_bus_scan_register_devices+0xc4/0x13c
>  [c000000263607bd0] [c0000000126c96e4]
> __machine_initcall_pseries_vio_device_init+0x94/0xf0
>  [c000000263607c00] [c00000000e69467c] do_one_initcall+0x12c/0xaa8
>  [c000000263607cf0] [c00000001268b8a8]
> kernel_init_freeable+0xa48/0xba8
>  [c000000263607dd0] [c00000000e695f24] kernel_init+0x64/0x400
>  [c000000263607e50] [c00000000e68e0e4]
> ret_from_kernel_thread+0x5c/0x64
> 
> Fix this by creating separate notifier_block structs for each bus
> type.
> 
> Fixes: d6b9a81b2a45 ("powerpc: IOMMU fault injection")
> Reported-by: Nageswara R Sastry <rnsastry at linux.ibm.com>
> Signed-off-by: Russell Currey <ruscur at russell.cc>

Reviewed-by: Andrew Donnellan <ajd at linux.ibm.com>


-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd at linux.ibm.com   IBM Australia Limited