linux-kernel - Re: [PATCH] KVM: mmio: Fix use-after-free Read in kvm_vm_ioctl_unregister_coalesced

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Date:   Thu, 8 Jul 2021 18:43:05 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, Hulk Robot <hulkci@...wei.com>
Subject: Re: [PATCH] KVM: mmio: Fix use-after-free Read in
 kvm_vm_ioctl_unregister_coalesced_mmio

On 26/06/21 09:03, Kefeng Wang wrote:
> BUG: KASAN: use-after-free in kvm_vm_ioctl_unregister_coalesced_mmio+0x7c/0x1ec arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:183
> Read of size 8 at addr ffff0000c03a2500 by task syz-executor083/4269
> 
> CPU: 5 PID: 4269 Comm: syz-executor083 Not tainted 5.10.0 #7
> Hardware name: linux,dummy-virt (DT)
> Call trace:
>   dump_backtrace+0x0/0x2d0 arch/arm64/kernel/stacktrace.c:132
>   show_stack+0x28/0x34 arch/arm64/kernel/stacktrace.c:196
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x110/0x164 lib/dump_stack.c:118
>   print_address_description+0x78/0x5c8 mm/kasan/report.c:385
>   __kasan_report mm/kasan/report.c:545 [inline]
>   kasan_report+0x148/0x1e4 mm/kasan/report.c:562
>   check_memory_region_inline mm/kasan/generic.c:183 [inline]
>   __asan_load8+0xb4/0xbc mm/kasan/generic.c:252
>   kvm_vm_ioctl_unregister_coalesced_mmio+0x7c/0x1ec arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:183
>   kvm_vm_ioctl+0xe30/0x14c4 arch/arm64/kvm/../../../virt/kvm/kvm_main.c:3755
>   vfs_ioctl fs/ioctl.c:48 [inline]
>   __do_sys_ioctl fs/ioctl.c:753 [inline]
>   __se_sys_ioctl fs/ioctl.c:739 [inline]
>   __arm64_sys_ioctl+0xf88/0x131c fs/ioctl.c:739
>   __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
>   invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
>   el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
>   do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:220
>   el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
>   el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
>   el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670
> 
> Allocated by task 4269:
>   stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
>   kasan_save_stack mm/kasan/common.c:48 [inline]
>   kasan_set_track mm/kasan/common.c:56 [inline]
>   __kasan_kmalloc+0xdc/0x120 mm/kasan/common.c:461
>   kasan_kmalloc+0xc/0x14 mm/kasan/common.c:475
>   kmem_cache_alloc_trace include/linux/slab.h:450 [inline]
>   kmalloc include/linux/slab.h:552 [inline]
>   kzalloc include/linux/slab.h:664 [inline]
>   kvm_vm_ioctl_register_coalesced_mmio+0x78/0x1cc arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:146
>   kvm_vm_ioctl+0x7e8/0x14c4 arch/arm64/kvm/../../../virt/kvm/kvm_main.c:3746
>   vfs_ioctl fs/ioctl.c:48 [inline]
>   __do_sys_ioctl fs/ioctl.c:753 [inline]
>   __se_sys_ioctl fs/ioctl.c:739 [inline]
>   __arm64_sys_ioctl+0xf88/0x131c fs/ioctl.c:739
>   __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
>   invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
>   el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
>   do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:220
>   el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
>   el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
>   el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670
> 
> Freed by task 4269:
>   stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
>   kasan_save_stack mm/kasan/common.c:48 [inline]
>   kasan_set_track+0x38/0x6c mm/kasan/common.c:56
>   kasan_set_free_info+0x20/0x40 mm/kasan/generic.c:355
>   __kasan_slab_free+0x124/0x150 mm/kasan/common.c:422
>   kasan_slab_free+0x10/0x1c mm/kasan/common.c:431
>   slab_free_hook mm/slub.c:1544 [inline]
>   slab_free_freelist_hook mm/slub.c:1577 [inline]
>   slab_free mm/slub.c:3142 [inline]
>   kfree+0x104/0x38c mm/slub.c:4124
>   coalesced_mmio_destructor+0x94/0xa4 arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:102
>   kvm_iodevice_destructor include/kvm/iodev.h:61 [inline]
>   kvm_io_bus_unregister_dev+0x248/0x280 arch/arm64/kvm/../../../virt/kvm/kvm_main.c:4374
>   kvm_vm_ioctl_unregister_coalesced_mmio+0x158/0x1ec arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:186
>   kvm_vm_ioctl+0xe30/0x14c4 arch/arm64/kvm/../../../virt/kvm/kvm_main.c:3755
>   vfs_ioctl fs/ioctl.c:48 [inline]
>   __do_sys_ioctl fs/ioctl.c:753 [inline]
>   __se_sys_ioctl fs/ioctl.c:739 [inline]
>   __arm64_sys_ioctl+0xf88/0x131c fs/ioctl.c:739
>   __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
>   invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
>   el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
>   do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:220
>   el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
>   el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
>   el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670
> 
> If kvm_io_bus_unregister_dev() return -ENOMEM, we already call kvm_iodevice_destructor()
> inside this function to delete 'struct kvm_coalesced_mmio_dev *dev' from list
> and free the dev, but kvm_iodevice_destructor() is called again, it will lead
> the above issue.
> 
> Let's check the the return value of kvm_io_bus_unregister_dev(), only call
> kvm_iodevice_destructor() if the return value is 0.
> 
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: kvm@...r.kernel.org
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@...wei.com>
> ---
>   virt/kvm/coalesced_mmio.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
> index f08f5e82460b..0be80c213f7f 100644
> --- a/virt/kvm/coalesced_mmio.c
> +++ b/virt/kvm/coalesced_mmio.c
> @@ -186,7 +186,6 @@ int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
>   		    coalesced_mmio_in_range(dev, zone->addr, zone->size)) {
>   			r = kvm_io_bus_unregister_dev(kvm,
>   				zone->pio ? KVM_PIO_BUS : KVM_MMIO_BUS, &dev->dev);
> -			kvm_iodevice_destructor(&dev->dev);
>   
>   			/*
>   			 * On failure, unregister destroys all devices on the
> @@ -196,6 +195,7 @@ int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
>   			 */
>   			if (r)
>   				break;
> +			kvm_iodevice_destructor(&dev->dev);
>   		}
>   	}
>   
> 

Queued, thanks.

Paolo