diff options
| author | Sean Christopherson <sean.j.christopherson@intel.com> | 2020-01-09 14:58:55 -0500 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-01-27 19:59:59 +0100 |
| commit | 6ad1e29fe0aba843dfffc714fced0ef6a2e19502 (patch) | |
| tree | 5cad93a7b21f8e66ed2d6b219af16652fb565044 /virt | |
| parent | fcfbc617547fc6d9552cb6c1c563b6a90ee98085 (diff) | |
| download | lwn-6ad1e29fe0aba843dfffc714fced0ef6a2e19502.tar.gz lwn-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')
| -rw-r--r-- | virt/kvm/kvm_main.c | 21 |
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, |