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authorSean Christopherson <sean.j.christopherson@intel.com>2020-01-09 14:58:55 -0500
committerPaolo Bonzini <pbonzini@redhat.com>2020-01-27 19:59:59 +0100
commit6ad1e29fe0aba843dfffc714fced0ef6a2e19502 (patch)
tree5cad93a7b21f8e66ed2d6b219af16652fb565044 /virt/kvm/kvm_main.c
parentKVM: Check for a bad hva before dropping into the ghc slow path (diff)
downloadlinux-dev-6ad1e29fe0aba843dfffc714fced0ef6a2e19502.tar.xz
linux-dev-6ad1e29fe0aba843dfffc714fced0ef6a2e19502.zip
KVM: Clean up __kvm_gfn_to_hva_cache_init() and its callers
Barret reported a (technically benign) bug where nr_pages_avail can be accessed without being initialized if gfn_to_hva_many() fails. virt/kvm/kvm_main.c:2193:13: warning: 'nr_pages_avail' may be used uninitialized in this function [-Wmaybe-uninitialized] Rather than simply squashing the warning by initializing nr_pages_avail, fix the underlying issues by reworking __kvm_gfn_to_hva_cache_init() to return immediately instead of continuing on. Now that all callers check the result and/or bail immediately on a bad hva, there's no need to explicitly nullify the memslot on error. Reported-by: Barret Rhoden <brho@google.com> Fixes: f1b9dd5eb86c ("kvm: Disallow wraparound in kvm_gfn_to_hva_cache_init") Cc: Jim Mattson <jmattson@google.com> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt/kvm/kvm_main.c')
-rw-r--r--virt/kvm/kvm_main.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e8be79db2e0a..7fa56ccdbe50 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2130,33 +2130,36 @@ static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots,
gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT;
gfn_t nr_pages_needed = end_gfn - start_gfn + 1;
gfn_t nr_pages_avail;
- int r = start_gfn <= end_gfn ? 0 : -EINVAL;
- ghc->gpa = gpa;
+ /* Update ghc->generation before performing any error checks. */
ghc->generation = slots->generation;
- ghc->len = len;
- ghc->hva = KVM_HVA_ERR_BAD;
+
+ if (start_gfn > end_gfn) {
+ ghc->hva = KVM_HVA_ERR_BAD;
+ return -EINVAL;
+ }
/*
* If the requested region crosses two memslots, we still
* verify that the entire region is valid here.
*/
- while (!r && start_gfn <= end_gfn) {
+ for ( ; start_gfn <= end_gfn; start_gfn += nr_pages_avail) {
ghc->memslot = __gfn_to_memslot(slots, start_gfn);
ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn,
&nr_pages_avail);
if (kvm_is_error_hva(ghc->hva))
- r = -EFAULT;
- start_gfn += nr_pages_avail;
+ return -EFAULT;
}
/* Use the slow path for cross page reads and writes. */
- if (!r && nr_pages_needed == 1)
+ if (nr_pages_needed == 1)
ghc->hva += offset;
else
ghc->memslot = NULL;
- return r;
+ ghc->gpa = gpa;
+ ghc->len = len;
+ return 0;
}
int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,