| Message ID | 20140421132601.GA13615@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 21/04/14 15:26, Oleg Nesterov wrote: > get_user_pages(mm) is simply wrong if mm->mm_users == 0 and exit_mmap/etc > was already called (or is in progress), mm->mm_count can only pin mm->pgd > and mm_struct itself. > > Change kvm_setup_async_pf/async_pf_execute to inc/dec mm->mm_users. > > kvm_create_vm/kvm_destroy_vm play with ->mm_count too but this case looks > fine at first glance, it seems that this ->mm is only used to verify that > current->mm == kvm->mm. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> This looks fine, from what I can tell. The old code has the problem mentioned in your patch description, so your version is probably better. > --- > virt/kvm/async_pf.c | 8 ++++---- > 1 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c > index 0ced4f3..cda703e 100644 > --- a/virt/kvm/async_pf.c > +++ b/virt/kvm/async_pf.c > @@ -99,7 +99,7 @@ static void async_pf_execute(struct work_struct *work) > if (waitqueue_active(&vcpu->wq)) > wake_up_interruptible(&vcpu->wq); > > - mmdrop(mm); > + mmput(mm); > kvm_put_kvm(vcpu->kvm); > } > > @@ -116,7 +116,7 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu) > flush_work(&work->work); > #else > if (cancel_work_sync(&work->work)) { > - mmdrop(work->mm); > + mmput(work->mm); > kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */ > kmem_cache_free(async_pf_cache, work); > } > @@ -181,7 +181,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva, > work->addr = hva; > work->arch = *arch; > work->mm = current->mm; > - atomic_inc(&work->mm->mm_count); > + atomic_inc(&work->mm->mm_users); > kvm_get_kvm(work->vcpu->kvm); > > /* this can't really happen otherwise gfn_to_pfn_async > @@ -199,7 +199,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva, > return 1; > retry_sync: > kvm_put_kvm(work->vcpu->kvm); > - mmdrop(work->mm); > + mmput(work->mm); > kmem_cache_free(async_pf_cache, work); > return 0; > } > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c index 0ced4f3..cda703e 100644 --- a/virt/kvm/async_pf.c +++ b/virt/kvm/async_pf.c @@ -99,7 +99,7 @@ static void async_pf_execute(struct work_struct *work) if (waitqueue_active(&vcpu->wq)) wake_up_interruptible(&vcpu->wq); - mmdrop(mm); + mmput(mm); kvm_put_kvm(vcpu->kvm); } @@ -116,7 +116,7 @@ void kvm_clear_async_pf_completion_queue(struct kvm_vcpu *vcpu) flush_work(&work->work); #else if (cancel_work_sync(&work->work)) { - mmdrop(work->mm); + mmput(work->mm); kvm_put_kvm(vcpu->kvm); /* == work->vcpu->kvm */ kmem_cache_free(async_pf_cache, work); } @@ -181,7 +181,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva, work->addr = hva; work->arch = *arch; work->mm = current->mm; - atomic_inc(&work->mm->mm_count); + atomic_inc(&work->mm->mm_users); kvm_get_kvm(work->vcpu->kvm); /* this can't really happen otherwise gfn_to_pfn_async @@ -199,7 +199,7 @@ int kvm_setup_async_pf(struct kvm_vcpu *vcpu, gva_t gva, unsigned long hva, return 1; retry_sync: kvm_put_kvm(work->vcpu->kvm); - mmdrop(work->mm); + mmput(work->mm); kmem_cache_free(async_pf_cache, work); return 0; }
get_user_pages(mm) is simply wrong if mm->mm_users == 0 and exit_mmap/etc was already called (or is in progress), mm->mm_count can only pin mm->pgd and mm_struct itself. Change kvm_setup_async_pf/async_pf_execute to inc/dec mm->mm_users. kvm_create_vm/kvm_destroy_vm play with ->mm_count too but this case looks fine at first glance, it seems that this ->mm is only used to verify that current->mm == kvm->mm. Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- virt/kvm/async_pf.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-)