• Gustavo A. R. Silva's avatar
    KVM: arm/arm64: vgic: Fix off-by-one bug in vgic_get_irq() · 70bf6988
    Gustavo A. R. Silva authored
    commit c23b2e6f upstream.
    
    When using the nospec API, it should be taken into account that:
    
    "...if the CPU speculates past the bounds check then
     * array_index_nospec() will clamp the index within the range of [0,
     * size)."
    
    The above is part of the header for macro array_index_nospec() in
    linux/nospec.h
    
    Now, in this particular case, if intid evaluates to exactly VGIC_MAX_SPI
    or to exaclty VGIC_MAX_PRIVATE, the array_index_nospec() macro ends up
    returning VGIC_MAX_SPI - 1 or VGIC_MAX_PRIVATE - 1 respectively, instead
    of VGIC_MAX_SPI or VGIC_MAX_PRIVATE, which, based on the original logic:
    
    	/* SGIs and PPIs */
    	if (intid <= VGIC_MAX_PRIVATE)
     		return &vcpu->arch.vgic_cpu.private_irqs[intid];
    
     	/* SPIs */
    	if (intid <= VGIC_MAX_SPI)
     		return &kvm->arch.vgic.spis[intid - VGIC_NR_PRIVATE_IRQS];
    
    are valid values for intid.
    
    Fix this by calling array_index_nospec() macro with VGIC_MAX_PRIVATE + 1
    and VGIC_MAX_SPI + 1 as arguments for its parameter size.
    
    Fixes: 41b87599 ("KVM: arm/arm64: vgic: fix possible spectre-v1 in vgic_get_irq()")
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
    [dropped the SPI part which was fixed separately]
    Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    70bf6988
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