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    Subject[PATCH AUTOSEL 4.20 260/304] kvm: Change offset in kvm_write_guest_offset_cached to unsigned
    Date
    From: Jim Mattson <jmattson@google.com>

    [ Upstream commit 7a86dab8cf2f0fdf508f3555dddfc236623bff60 ]

    Since the offset is added directly to the hva from the
    gfn_to_hva_cache, a negative offset could result in an out of bounds
    write. The existing BUG_ON only checks for addresses beyond the end of
    the gfn_to_hva_cache, not for addresses before the start of the
    gfn_to_hva_cache.

    Note that all current call sites have non-negative offsets.

    Fixes: 4ec6e8636256 ("kvm: Introduce kvm_write_guest_offset_cached()")
    Reported-by: Cfir Cohen <cfir@google.com>
    Signed-off-by: Jim Mattson <jmattson@google.com>
    Reviewed-by: Cfir Cohen <cfir@google.com>
    Reviewed-by: Peter Shier <pshier@google.com>
    Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
    Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
    Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    include/linux/kvm_host.h | 3 ++-
    virt/kvm/kvm_main.c | 3 ++-
    2 files changed, 4 insertions(+), 2 deletions(-)

    diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    index c926698040e0..a03d5e264e5e 100644
    --- a/include/linux/kvm_host.h
    +++ b/include/linux/kvm_host.h
    @@ -694,7 +694,8 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
    int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
    void *data, unsigned long len);
    int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
    - void *data, int offset, unsigned long len);
    + void *data, unsigned int offset,
    + unsigned long len);
    int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
    gpa_t gpa, unsigned long len);
    int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index 2679e476b6c3..065ee2fb4034 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -1965,7 +1965,8 @@ int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
    EXPORT_SYMBOL_GPL(kvm_gfn_to_hva_cache_init);

    int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
    - void *data, int offset, unsigned long len)
    + void *data, unsigned int offset,
    + unsigned long len)
    {
    struct kvm_memslots *slots = kvm_memslots(kvm);
    int r;
    --
    2.19.1
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