• Zenghui Yu's avatar
    KVM: arm64: vgic-v3: Retire all pending LPIs on vcpu destroy · 969ce8b5
    Zenghui Yu authored
    It's likely that the vcpu fails to handle all virtual interrupts if
    userspace decides to destroy it, leaving the pending ones stay in the
    ap_list. If the un-handled one is a LPI, its vgic_irq structure will
    be eventually leaked because of an extra refcount increment in
    vgic_queue_irq_unlock().
    
    This was detected by kmemleak on almost every guest destroy, the
    backtrace is as follows:
    
    unreferenced object 0xffff80725aed5500 (size 128):
    comm "CPU 5/KVM", pid 40711, jiffies 4298024754 (age 166366.512s)
    hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 08 01 a9 73 6d 80 ff ff ...........sm...
    c8 61 ee a9 00 20 ff ff 28 1e 55 81 6c 80 ff ff .a... ..(.U.l...
    backtrace:
    [<000000004bcaa122>] kmem_cache_alloc_trace+0x2dc/0x418
    [<0000000069c7dabb>] vgic_add_lpi+0x88/0x418
    [<00000000bfefd5c5>] vgic_its_cmd_handle_mapi+0x4dc/0x588
    [<00000000cf993975>] vgic_its_process_commands.part.5+0x484/0x1198
    [<000000004bd3f8e3>] vgic_its_process_commands+0x50/0x80
    [<00000000b9a65b2b>] vgic_mmio_write_its_cwriter+0xac/0x108
    [<0000000009641ebb>] dispatch_mmio_write+0xd0/0x188
    [<000000008f79d288>] __kvm_io_bus_write+0x134/0x240
    [<00000000882f39ac>] kvm_io_bus_write+0xe0/0x150
    [<0000000078197602>] io_mem_abort+0x484/0x7b8
    [<0000000060954e3c>] kvm_handle_guest_abort+0x4cc/0xa58
    [<00000000e0d0cd65>] handle_exit+0x24c/0x770
    [<00000000b44a7fad>] kvm_arch_vcpu_ioctl_run+0x460/0x1988
    [<0000000025fb897c>] kvm_vcpu_ioctl+0x4f8/0xee0
    [<000000003271e317>] do_vfs_ioctl+0x160/0xcd8
    [<00000000e7f39607>] ksys_ioctl+0x98/0xd8
    
    Fix it by retiring all pending LPIs in the ap_list on the destroy path.
    
    p.s. I can also reproduce it on a normal guest shutdown. It is because
    userspace still send LPIs to vcpu (through KVM_SIGNAL_MSI ioctl) while
    the guest is being shutdown and unable to handle it. A little strange
    though and haven't dig further...
    Reviewed-by: default avatarJames Morse <james.morse@arm.com>
    Signed-off-by: default avatarZenghui Yu <yuzenghui@huawei.com>
    [maz: moved the distributor deallocation down to avoid an UAF splat]
    Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
    Link: https://lore.kernel.org/r/20200414030349.625-2-yuzenghui@huawei.com
    969ce8b5
vgic-init.c 13.3 KB