This is a note to let you know that I've just added the patch titled

KVM: mmu: Fix overlap between public and private memslots

to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: kvm-mmu-fix-overlap-between-public-and-private-memslots.patch and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From b28676bb8ae4569cced423dc2a88f7cb319d5379 Mon Sep 17 00:00:00 2001

From: Wanpeng Li wanpeng.li@hotmail.com Date: Tue, 13 Feb 2018 15:36:00 +0100 Subject: KVM: mmu: Fix overlap between public and private memslots MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

From: Wanpeng Li wanpeng.li@hotmail.com

commit b28676bb8ae4569cced423dc2a88f7cb319d5379 upstream.

Reported by syzkaller:

pte_list_remove: ffff9714eb1f8078 0->BUG ------------[ cut here ]------------ kernel BUG at arch/x86/kvm/mmu.c:1157! invalid opcode: 0000 [#1] SMP RIP: 0010:pte_list_remove+0x11b/0x120 [kvm] Call Trace: drop_spte+0x83/0xb0 [kvm] mmu_page_zap_pte+0xcc/0xe0 [kvm] kvm_mmu_prepare_zap_page+0x81/0x4a0 [kvm] kvm_mmu_invalidate_zap_all_pages+0x159/0x220 [kvm] kvm_arch_flush_shadow_all+0xe/0x10 [kvm] kvm_mmu_notifier_release+0x6c/0xa0 [kvm] ? kvm_mmu_notifier_release+0x5/0xa0 [kvm] __mmu_notifier_release+0x79/0x110 ? __mmu_notifier_release+0x5/0x110 exit_mmap+0x15a/0x170 ? do_exit+0x281/0xcb0 mmput+0x66/0x160 do_exit+0x2c9/0xcb0 ? __context_tracking_exit.part.5+0x4a/0x150 do_group_exit+0x50/0xd0 SyS_exit_group+0x14/0x20 do_syscall_64+0x73/0x1f0 entry_SYSCALL64_slow_path+0x25/0x25

The reason is that when creates new memslot, there is no guarantee for new memslot not overlap with private memslots. This can be triggered by the following program:

#include <fcntl.h> #include <pthread.h> #include <setjmp.h> #include <signal.h> #include <stddef.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/ioctl.h> #include <sys/stat.h> #include <sys/syscall.h> #include <sys/types.h> #include <unistd.h> #include <linux/kvm.h>

long r[16];

int main() { void *p = valloc(0x4000);

r[2] = open("/dev/kvm", 0); r[3] = ioctl(r[2], KVM_CREATE_VM, 0x0ul);

uint64_t addr = 0xf000; ioctl(r[3], KVM_SET_IDENTITY_MAP_ADDR, &addr); r[6] = ioctl(r[3], KVM_CREATE_VCPU, 0x0ul); ioctl(r[3], KVM_SET_TSS_ADDR, 0x0ul); ioctl(r[6], KVM_RUN, 0); ioctl(r[6], KVM_RUN, 0);

struct kvm_userspace_memory_region mr = { .slot = 0, .flags = KVM_MEM_LOG_DIRTY_PAGES, .guest_phys_addr = 0xf000, .memory_size = 0x4000, .userspace_addr = (uintptr_t) p }; ioctl(r[3], KVM_SET_USER_MEMORY_REGION, &mr); return 0; }

This patch fixes the bug by not adding a new memslot even if it overlaps with private memslots.

Reported-by: Dmitry Vyukov dvyukov@google.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Radim Krčmář rkrcmar@redhat.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Eric Biggers ebiggers3@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Wanpeng Li wanpeng.li@hotmail.com --- virt/kvm/kvm_main.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -974,8 +974,7 @@ int __kvm_set_memory_region(struct kvm * /* Check for overlaps */ r = -EEXIST; kvm_for_each_memslot(slot, __kvm_memslots(kvm, as_id)) { - if ((slot->id >= KVM_USER_MEM_SLOTS) || - (slot->id == id)) + if (slot->id == id) continue; if (!((base_gfn + npages <= slot->base_gfn) || (base_gfn >= slot->base_gfn + slot->npages)))

Patches currently in stable-queue which might be from wanpeng.li@hotmail.com are

queue-4.15/kvm-mmu-fix-overlap-between-public-and-private-memslots.patch