On 09/30/2009 02:04 PM, Arnd Bergmann wrote:
On Tuesday 29 September 2009, Avi Kivity wrote:r = -EINVAL; if (log->slot>= KVM_MEMORY_SLOTS) @@ -718,8 +719,15 @@ int kvm_get_dirty_log(struct kvm *kvm, for (i = 0; !any&& i< n/sizeof(long); ++i) any = memslot->dirty_bitmap[i]; +#if defined(__BIG_ENDIAN)&& defined(CONFIG_64BIT) + /* Need to convert user pointers */ + if (test_thread_flag(TIF_32BIT)) + target_bm = (void*)((u64)log->dirty_bitmap>> 32); + else +#endif + target_bm = log->dirty_bitmap; r = -EFAULT; - if (copy_to_user(log->dirty_bitmap, memslot->dirty_bitmap, n)) + if (copy_to_user(target_bm, memslot->dirty_bitmap, n)) goto out; if (any)Ah, that's much better. Plus a mental note not to put pointers in user-visible structures in the future. This can serve as a reminder :)It's still broken on s390, which 1. uses TIF_31BIT instead of TIF_32BIT 2. needs to call compat_ptr() to do a real conversion instead of a cast The TIF_32BIT method is also not reliable. E.g. on x86_64 you are supposed to get the 32 bit ABI when calling through INT80 instead of syscall/sysenter, independent of the value of TIF_32BIT. A better way to do this is to add a separate compat_ioctl() method that converts this for you. The patch below is an example for the canonical way to do this. Not tested! Signed-off-by: Arnd Bergmann<arnd@xxxxxxxx> --- diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 897bff3..20f88ad 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2297,6 +2297,49 @@ out: return r; } +#ifdef CONFIG_COMPAT +struct compat_kvm_dirty_log { + __u32 slot; + __u32 padding1; + union { + compat_uptr_t dirty_bitmap; /* one bit per page */ + __u64 padding2; + }; +}; + +static long kvm_vm_compat_ioctl(struct file *filp, + unsigned int ioctl, unsigned long arg) +{ + struct kvm *kvm = filp->private_data; + int r; + + if (kvm->mm != current->mm) + return -EIO; + switch (ioctl) { + case KVM_GET_DIRTY_LOG: { + struct compat_kvm_dirty_log compat_log; + struct kvm_dirty_log log; + + r = -EFAULT; + if (copy_from_user(&compat_log, (void __user *)arg, sizeof log)) + goto out; + log.slot = compat_log.slot; + log.padding1 = compat_log.padding1; + log.padding2 = compat_log.padding2; + log.dirty_bitmap = compat_ptr(compat_log.dirty_bitmap); + + r = kvm_vm_ioctl_get_dirty_log(kvm,&log.log); + if (r) + goto out; + break; + default: + r = kvm_vm_ioctl(filp, ioctl, arg); + } + + return r; +} +#endif + static int kvm_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) { struct page *page[1]; @@ -2331,7 +2374,7 @@ static int kvm_vm_mmap(struct file *file, struct vm_area_struct *vma) static struct file_operations kvm_vm_fops = { .release = kvm_vm_release, .unlocked_ioctl = kvm_vm_ioctl, - .compat_ioctl = kvm_vm_ioctl, + .compat_ioctl = kvm_vm_compat_ioctl, .mmap = kvm_vm_mmap, };
This is a bit painful - I tried to avoid compat_ioctl. Maybe it's better to have dirty_bitmap_virt, given no existing users are impacted.
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