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Subject[PATCH 4.14 134/205] kvm: Change offset in kvm_write_guest_offset_cached to unsigned
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

[ 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 b6962ae6237e..4f7f19c1dc0a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -685,7 +685,8 @@ 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 4f35f0dfe681..bbc34e87d88f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1962,7 +1962,8 @@ 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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