| Message ID | 20200109195855.17353-1-brho@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: squelch uninitialized variable warning | expand |
On Thu, Jan 09, 2020 at 02:58:55PM -0500, Barret Rhoden wrote: > If gfn_to_hva_many() fails, __kvm_gfn_to_hva_cache_init() will return an > error. Before it does, it might use nr_pages_avail, which my compiler > complained about: > > virt/kvm/kvm_main.c:2193:13: warning: 'nr_pages_avail' may be > used uninitialized in this function [-Wmaybe-uninitialized] > > start_gfn += nr_pages_avail; Ugh, this whole flow is funky. The change is correct, and is certainly the minimal change if we want to backport this to stable, but IMO it's putting lipstick on a pig. I'd rather fix the underlying issues and make the code more readable in the process. I'll send a patch. If we want to take this as a minimal fix, Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> > Signed-off-by: Barret Rhoden <brho@google.com> > --- > virt/kvm/kvm_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index d9aced677ddd..f8249b153d33 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2172,7 +2172,7 @@ static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots, > gfn_t start_gfn = gpa >> PAGE_SHIFT; > gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT; > gfn_t nr_pages_needed = end_gfn - start_gfn + 1; > - gfn_t nr_pages_avail; > + gfn_t nr_pages_avail = 0; > int r = start_gfn <= end_gfn ? 0 : -EINVAL; > > ghc->gpa = gpa; > -- > 2.25.0.rc1.283.g88dfdc4193-goog >
On 09/01/20 23:04, Sean Christopherson wrote:
> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Thanks, I queued it so that at least it gets to stable.
Paolo
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index d9aced677ddd..f8249b153d33 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2172,7 +2172,7 @@ static int __kvm_gfn_to_hva_cache_init(struct kvm_memslots *slots, gfn_t start_gfn = gpa >> PAGE_SHIFT; gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT; gfn_t nr_pages_needed = end_gfn - start_gfn + 1; - gfn_t nr_pages_avail; + gfn_t nr_pages_avail = 0; int r = start_gfn <= end_gfn ? 0 : -EINVAL; ghc->gpa = gpa;
If gfn_to_hva_many() fails, __kvm_gfn_to_hva_cache_init() will return an error. Before it does, it might use nr_pages_avail, which my compiler complained about: virt/kvm/kvm_main.c:2193:13: warning: 'nr_pages_avail' may be used uninitialized in this function [-Wmaybe-uninitialized] start_gfn += nr_pages_avail; Signed-off-by: Barret Rhoden <brho@google.com> --- virt/kvm/kvm_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)