[v2] kvm: Change offset in kvm_write_guest_offset_cached to unsigned
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Message ID 20181214223443.153614-1-jmattson@google.com
State New
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Series
  • [v2] kvm: Change offset in kvm_write_guest_offset_cached to unsigned
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Commit Message

Jim Mattson Dec. 14, 2018, 10:34 p.m. UTC
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>
---
 include/linux/kvm_host.h | 3 ++-
 virt/kvm/kvm_main.c      | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

Comments

Radim Krčmář Dec. 20, 2018, 8:14 p.m. UTC | #1
2018-12-14 14:34-0800, Jim Mattson:
> 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>
> ---

Queued, thanks.

Patch
diff mbox series

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index c926698040e0d..a03d5e264e5e7 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 2679e476b6c39..065ee2fb40340 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;