CVE-2021-47230

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> KVM: x86: Immediately reset the MMU context when the SMM flag is cleared<br /> <br /> Immediately reset the MMU context when the vCPU&amp;#39;s SMM flag is cleared so<br /> that the SMM flag in the MMU role is always synchronized with the vCPU&amp;#39;s<br /> flag. If RSM fails (which isn&amp;#39;t correctly emulated), KVM will bail<br /> without calling post_leave_smm() and leave the MMU in a bad state.<br /> <br /> The bad MMU role can lead to a NULL pointer dereference when grabbing a<br /> shadow page&amp;#39;s rmap for a page fault as the initial lookups for the gfn<br /> will happen with the vCPU&amp;#39;s SMM flag (=0), whereas the rmap lookup will<br /> use the shadow page&amp;#39;s SMM flag, which comes from the MMU (=1). SMM has<br /> an entirely different set of memslots, and so the initial lookup can find<br /> a memslot (SMM=0) and then explode on the rmap memslot lookup (SMM=1).<br /> <br /> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN<br /> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]<br /> CPU: 1 PID: 8410 Comm: syz-executor382 Not tainted 5.13.0-rc5-syzkaller #0<br /> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011<br /> RIP: 0010:__gfn_to_rmap arch/x86/kvm/mmu/mmu.c:935 [inline]<br /> RIP: 0010:gfn_to_rmap+0x2b0/0x4d0 arch/x86/kvm/mmu/mmu.c:947<br /> Code: 80 3c 20 00 74 08 4c 89 ff e8 f1 79 a9 00 4c 89 fb 4d 8b 37 44<br /> RSP: 0018:ffffc90000ffef98 EFLAGS: 00010246<br /> RAX: 0000000000000000 RBX: ffff888015b9f414 RCX: ffff888019669c40<br /> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001<br /> RBP: 0000000000000001 R08: ffffffff811d9cdb R09: ffffed10065a6002<br /> R10: ffffed10065a6002 R11: 0000000000000000 R12: dffffc0000000000<br /> R13: 0000000000000003 R14: 0000000000000001 R15: 0000000000000000<br /> FS: 000000000124b300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000<br /> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033<br /> CR2: 0000000000000000 CR3: 0000000028e31000 CR4: 00000000001526e0<br /> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000<br /> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400<br /> Call Trace:<br /> rmap_add arch/x86/kvm/mmu/mmu.c:965 [inline]<br /> mmu_set_spte+0x862/0xe60 arch/x86/kvm/mmu/mmu.c:2604<br /> __direct_map arch/x86/kvm/mmu/mmu.c:2862 [inline]<br /> direct_page_fault+0x1f74/0x2b70 arch/x86/kvm/mmu/mmu.c:3769<br /> kvm_mmu_do_page_fault arch/x86/kvm/mmu.h:124 [inline]<br /> kvm_mmu_page_fault+0x199/0x1440 arch/x86/kvm/mmu/mmu.c:5065<br /> vmx_handle_exit+0x26/0x160 arch/x86/kvm/vmx/vmx.c:6122<br /> vcpu_enter_guest+0x3bdd/0x9630 arch/x86/kvm/x86.c:9428<br /> vcpu_run+0x416/0xc20 arch/x86/kvm/x86.c:9494<br /> kvm_arch_vcpu_ioctl_run+0x4e8/0xa40 arch/x86/kvm/x86.c:9722<br /> kvm_vcpu_ioctl+0x70f/0xbb0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3460<br /> vfs_ioctl fs/ioctl.c:51 [inline]<br /> __do_sys_ioctl fs/ioctl.c:1069 [inline]<br /> __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:1055<br /> do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47<br /> entry_SYSCALL_64_after_hwframe+0x44/0xae<br /> RIP: 0033:0x440ce9