| Message ID | 20240723000211.3352304-1-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/mmu: Check that root is valid/loaded when pre-faulting SPTEs | expand |
On 23/07/2024 12:02 pm, Sean Christopherson wrote: > Error out if kvm_mmu_reload() fails when pre-faulting memory, as trying to > fault-in SPTEs will fail miserably due to root.hpa pointing at garbage. > > Note, kvm_mmu_reload() can return -EIO and thus trigger the WARN on -EIO > in kvm_vcpu_pre_fault_memory(), but all such paths also WARN, i.e. the > WARN isn't user-triggerable and won't run afoul of warn-on-panic because > the kernel would already be panicking. > > BUG: unable to handle page fault for address: 000029ffffffffe8 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: Oops: 0000 [#1] PREEMPT SMP > CPU: 22 PID: 1069 Comm: pre_fault_memor Not tainted 6.10.0-rc7-332d2c1d713e-next-vm #548 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 > RIP: 0010:is_page_fault_stale+0x3e/0xe0 [kvm] > RSP: 0018:ffffc9000114bd48 EFLAGS: 00010206 > RAX: 00003fffffffffc0 RBX: ffff88810a07c080 RCX: ffffc9000114bd78 > RDX: ffff88810a07c080 RSI: ffffea0000000000 RDI: ffff88810a07c080 > RBP: ffffc9000114bd78 R08: 00007fa3c8c00000 R09: 8000000000000225 > R10: ffffea00043d7d80 R11: 0000000000000000 R12: ffff88810a07c080 > R13: 0000000100000000 R14: ffffc9000114be58 R15: 0000000000000000 > FS: 00007fa3c9da0740(0000) GS:ffff888277d80000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000029ffffffffe8 CR3: 000000011d698000 CR4: 0000000000352eb0 > Call Trace: > <TASK> > kvm_tdp_page_fault+0xcc/0x160 [kvm] > kvm_mmu_do_page_fault+0xfb/0x1f0 [kvm] > kvm_arch_vcpu_pre_fault_memory+0xd0/0x1a0 [kvm] > kvm_vcpu_ioctl+0x761/0x8c0 [kvm] > __x64_sys_ioctl+0x82/0xb0 > do_syscall_64+0x5b/0x160 > entry_SYSCALL_64_after_hwframe+0x4b/0x53 > </TASK> > Modules linked in: kvm_intel kvm > CR2: 000029ffffffffe8 > ---[ end trace 0000000000000000 ]--- > > Fixes: 6e01b7601dfe ("KVM: x86: Implement kvm_arch_vcpu_pre_fault_memory()") > Reported-by: syzbot+23786faffb695f17edaa@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/0000000000002b84dc061dd73544@google.com > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- Reviewed-by: Kai Huang <kai.huang@intel.com>
On Mon, 22 Jul 2024 17:02:11 -0700, Sean Christopherson wrote: > Error out if kvm_mmu_reload() fails when pre-faulting memory, as trying to > fault-in SPTEs will fail miserably due to root.hpa pointing at garbage. > > Note, kvm_mmu_reload() can return -EIO and thus trigger the WARN on -EIO > in kvm_vcpu_pre_fault_memory(), but all such paths also WARN, i.e. the > WARN isn't user-triggerable and won't run afoul of warn-on-panic because > the kernel would already be panicking. > > [...] Applied to kvm-x86 fixes, thanks! [1/1] KVM: x86/mmu: Check that root is valid/loaded when pre-faulting SPTEs https://github.com/kvm-x86/linux/commit/28cec7f08b8b -- https://github.com/kvm-x86/linux/tree/next
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 901be9e420a4..ee516baf3a31 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4747,7 +4747,9 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, * reload is efficient when called repeatedly, so we can do it on * every iteration. */ - kvm_mmu_reload(vcpu); + r = kvm_mmu_reload(vcpu); + if (r) + return r; if (kvm_arch_has_private_mem(vcpu->kvm) && kvm_mem_is_private(vcpu->kvm, gpa_to_gfn(range->gpa)))
Error out if kvm_mmu_reload() fails when pre-faulting memory, as trying to fault-in SPTEs will fail miserably due to root.hpa pointing at garbage. Note, kvm_mmu_reload() can return -EIO and thus trigger the WARN on -EIO in kvm_vcpu_pre_fault_memory(), but all such paths also WARN, i.e. the WARN isn't user-triggerable and won't run afoul of warn-on-panic because the kernel would already be panicking. BUG: unable to handle page fault for address: 000029ffffffffe8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] PREEMPT SMP CPU: 22 PID: 1069 Comm: pre_fault_memor Not tainted 6.10.0-rc7-332d2c1d713e-next-vm #548 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:is_page_fault_stale+0x3e/0xe0 [kvm] RSP: 0018:ffffc9000114bd48 EFLAGS: 00010206 RAX: 00003fffffffffc0 RBX: ffff88810a07c080 RCX: ffffc9000114bd78 RDX: ffff88810a07c080 RSI: ffffea0000000000 RDI: ffff88810a07c080 RBP: ffffc9000114bd78 R08: 00007fa3c8c00000 R09: 8000000000000225 R10: ffffea00043d7d80 R11: 0000000000000000 R12: ffff88810a07c080 R13: 0000000100000000 R14: ffffc9000114be58 R15: 0000000000000000 FS: 00007fa3c9da0740(0000) GS:ffff888277d80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000029ffffffffe8 CR3: 000000011d698000 CR4: 0000000000352eb0 Call Trace: <TASK> kvm_tdp_page_fault+0xcc/0x160 [kvm] kvm_mmu_do_page_fault+0xfb/0x1f0 [kvm] kvm_arch_vcpu_pre_fault_memory+0xd0/0x1a0 [kvm] kvm_vcpu_ioctl+0x761/0x8c0 [kvm] __x64_sys_ioctl+0x82/0xb0 do_syscall_64+0x5b/0x160 entry_SYSCALL_64_after_hwframe+0x4b/0x53 </TASK> Modules linked in: kvm_intel kvm CR2: 000029ffffffffe8 ---[ end trace 0000000000000000 ]--- Fixes: 6e01b7601dfe ("KVM: x86: Implement kvm_arch_vcpu_pre_fault_memory()") Reported-by: syzbot+23786faffb695f17edaa@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/0000000000002b84dc061dd73544@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> --- Haven't seen a reproducer from syzbot, but I verified by forcing the same root allocation failure (to generate the above splat). arch/x86/kvm/mmu/mmu.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) base-commit: 332d2c1d713e232e163386c35a3ba0c1b90df83f