During RH6.2 graphical installation the following oops is triggered: BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 IP: [<ffffffffa00bf172>] :kvm:gfn_to_rmap+0x3e/0x61 Pid: 4559, comm: qemu-system-x86 Not tainted RIP: 0010:[<ffffffffa00bf172>] [<ffffffffa00bf172>] :kvm:gfn_to_rmap+0x3e/0x61
Process qemu-system-x86 (pid: 4559, threadinfo ffff810220920000, task ffff81022e82b2f0) Stack: 0000000000217a4b ffff81021a48e9d8 ffff81021a48fa80 ffffffffa00bf240 ffff810220ab82f0 ffff81021a48e9d8 ffff81021a48fa80 000000000000013b ffff81022288c000 ffffffffa00bf3b7 000000000003aed3 ffff81022288c000 Call Trace: [<ffffffffa00bf240>] ? :kvm:rmap_remove+0xab/0x19d [<ffffffffa00bf3b7>] ? :kvm:kvm_mmu_zap_page+0x85/0x26e [<ffffffffa00bf8a5>] ? :kvm:kvm_mmu_zap_all+0x2b/0x46 [<ffffffffa00bb37c>] ? :kvm:kvm_arch_vm_ioctl+0x262/0x575 [<ffffffffa00b6fb8>] ? :kvm:kvm_read_guest+0x3f/0x7d [<ffffffffa00c19c9>] ? :kvm:paging32_walk_addr+0xac/0x262 [<ffffffffa00b6d7c>] ? :kvm:gfn_to_hva+0x9/0x5d [<ffffffffa00b6f44>] ? :kvm:kvm_read_guest_page+0x11/0x46 The problem is that KVM allows shadow pagetable entries that point to a removed memslot to exist. In this case the cirrus vram mapping was removed, and the NULL dereference happened during kvm_set_memory_alias()'s zap_all_pages(). Since a malicious guest could have a thread's root table inside the to-be-removed memslot, also guarantee there this is not the case before removal. This behaviour will also be useful for memory hotplugging. As a side note, RH 6.2 graphical installation still won't function (due to cirrus emulation bugs). Signed-off-by: Marcelo Tosatti <[EMAIL PROTECTED]> Index: kvm/arch/x86/kvm/x86.c =================================================================== --- kvm.orig/arch/x86/kvm/x86.c +++ kvm/arch/x86/kvm/x86.c @@ -4040,6 +4040,12 @@ int kvm_arch_set_memory_region(struct kv return 0; } +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot) +{ + kvm_mmu_zap_all(kvm); + return kvm_mmu_slot_has_shadowed_page(kvm, slot); +} + int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu) { return vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE Index: kvm/include/linux/kvm_host.h =================================================================== --- kvm.orig/include/linux/kvm_host.h +++ kvm/include/linux/kvm_host.h @@ -168,6 +168,7 @@ int kvm_arch_set_memory_region(struct kv struct kvm_userspace_memory_region *mem, struct kvm_memory_slot old, int user_alloc); +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot); gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn); struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn); unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn); Index: kvm/virt/kvm/kvm_main.c =================================================================== --- kvm.orig/virt/kvm/kvm_main.c +++ kvm/virt/kvm/kvm_main.c @@ -405,6 +405,12 @@ int __kvm_set_memory_region(struct kvm * if (mem->slot >= kvm->nmemslots) kvm->nmemslots = mem->slot + 1; + if (!npages) { + r = kvm_arch_destroy_memory_region(kvm, mem->slot); + if (r) + goto out_free; + } + *memslot = new; r = kvm_arch_set_memory_region(kvm, mem, old, user_alloc); Index: kvm/arch/ia64/kvm/kvm-ia64.c =================================================================== --- kvm.orig/arch/ia64/kvm/kvm-ia64.c +++ kvm/arch/ia64/kvm/kvm-ia64.c @@ -1455,6 +1455,10 @@ int kvm_arch_set_memory_region(struct kv return 0; } +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot) +{ + return 0; +} long kvm_arch_dev_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) Index: kvm/arch/powerpc/kvm/powerpc.c =================================================================== --- kvm.orig/arch/powerpc/kvm/powerpc.c +++ kvm/arch/powerpc/kvm/powerpc.c @@ -170,6 +170,11 @@ int kvm_arch_set_memory_region(struct kv return 0; } +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot) +{ + return 0; +} + struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id) { struct kvm_vcpu *vcpu; Index: kvm/arch/s390/kvm/kvm-s390.c =================================================================== --- kvm.orig/arch/s390/kvm/kvm-s390.c +++ kvm/arch/s390/kvm/kvm-s390.c @@ -675,6 +675,11 @@ int kvm_arch_set_memory_region(struct kv return 0; } +int kvm_arch_destroy_memory_region(struct kvm *kvm, int slot) +{ + return 0; +} + gfn_t unalias_gfn(struct kvm *kvm, gfn_t gfn) { return gfn; Index: kvm/arch/x86/kvm/mmu.c =================================================================== --- kvm.orig/arch/x86/kvm/mmu.c +++ kvm/arch/x86/kvm/mmu.c @@ -1955,6 +1955,22 @@ void kvm_mmu_slot_remove_write_access(st } } +int kvm_mmu_slot_has_shadowed_page(struct kvm *kvm, int slot) +{ + struct kvm_mmu_page *sp; + int ret = 0; + + spin_lock(&kvm->mmu_lock); + list_for_each_entry(sp, &kvm->arch.active_mmu_pages, link) { + if (test_bit(slot, &sp->slot_bitmap)) { + ret = -EINVAL; + break; + } + } + spin_unlock(&kvm->mmu_lock); + return ret; +} + void kvm_mmu_zap_all(struct kvm *kvm) { struct kvm_mmu_page *sp, *node; Index: kvm/include/asm-x86/kvm_host.h =================================================================== --- kvm.orig/include/asm-x86/kvm_host.h +++ kvm/include/asm-x86/kvm_host.h @@ -457,6 +457,7 @@ void kvm_mmu_set_mask_ptes(u64 user_mask int kvm_mmu_reset_context(struct kvm_vcpu *vcpu); void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot); +int kvm_mmu_slot_has_shadowed_page(struct kvm *kvm, int slot); void kvm_mmu_zap_all(struct kvm *kvm); unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm); void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages); -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html