Greg Kurz 1d0c32ec3b KVM: PPC: Fix kernel crash with PR KVM ... With PR KVM, shutting down a VM causes the host kernel to crash: [ 314.219284] BUG: Unable to handle kernel data access on read at 0xc00800000176c638 [ 314.219299] Faulting instruction address: 0xc008000000d4ddb0 cpu 0x0: Vector: 300 (Data Access) at [c00000036da077a0] pc: c008000000d4ddb0: kvmppc_mmu_pte_flush_all+0x68/0xd0 [kvm_pr] lr: c008000000d4dd94: kvmppc_mmu_pte_flush_all+0x4c/0xd0 [kvm_pr] sp: c00000036da07a30 msr: 900000010280b033 dar: c00800000176c638 dsisr: 40000000 current = 0xc00000036d4c0000 paca = 0xc000000001a00000 irqmask: 0x03 irq_happened: 0x01 pid = 1992, comm = qemu-system-ppc Linux version 5.6.0-master-gku+ (greg@palmb) (gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)) #17 SMP Wed Mar 18 13:49:29 CET 2020 enter ? for help [c00000036da07ab0] c008000000d4fbe0 kvmppc_mmu_destroy_pr+0x28/0x60 [kvm_pr] [c00000036da07ae0] c0080000009eab8c kvmppc_mmu_destroy+0x34/0x50 [kvm] [c00000036da07b00] c0080000009e50c0 kvm_arch_vcpu_destroy+0x108/0x140 [kvm] [c00000036da07b30] c0080000009d1b50 kvm_vcpu_destroy+0x28/0x80 [kvm] [c00000036da07b60] c0080000009e4434 kvm_arch_destroy_vm+0xbc/0x190 [kvm] [c00000036da07ba0] c0080000009d9c2c kvm_put_kvm+0x1d4/0x3f0 [kvm] [c00000036da07c00] c0080000009da760 kvm_vm_release+0x38/0x60 [kvm] [c00000036da07c30] c000000000420be0 __fput+0xe0/0x310 [c00000036da07c90] c0000000001747a0 task_work_run+0x150/0x1c0 [c00000036da07cf0] c00000000014896c do_exit+0x44c/0xd00 [c00000036da07dc0] c0000000001492f4 do_group_exit+0x64/0xd0 [c00000036da07e00] c000000000149384 sys_exit_group+0x24/0x30 [c00000036da07e20] c00000000000b9d0 system_call+0x5c/0x68 This is caused by a use-after-free in kvmppc_mmu_pte_flush_all() which dereferences vcpu->arch.book3s which was previously freed by kvmppc_core_vcpu_free_pr(). This happens because kvmppc_mmu_destroy() is called after kvmppc_core_vcpu_free() since commit ff030fdf55 ("KVM: PPC: Move kvm_vcpu_init() invocation to common code"). The kvmppc_mmu_destroy() helper calls one of the following depending on the KVM backend: - kvmppc_mmu_destroy_hv() which does nothing (Book3s HV) - kvmppc_mmu_destroy_pr() which undoes the effects of kvmppc_mmu_init() (Book3s PR 32-bit) - kvmppc_mmu_destroy_pr() which undoes the effects of kvmppc_mmu_init() (Book3s PR 64-bit) - kvmppc_mmu_destroy_e500() which does nothing (BookE e500/e500mc) It turns out that this is only relevant to PR KVM actually. And both 32 and 64 backends need vcpu->arch.book3s to be valid when calling kvmppc_mmu_destroy_pr(). So instead of calling kvmppc_mmu_destroy() from kvm_arch_vcpu_destroy(), call kvmppc_mmu_destroy_pr() at the beginning of kvmppc_core_vcpu_free_pr(). This is consistent with kvmppc_mmu_init() being the last call in kvmppc_core_vcpu_create_pr(). For the same reason, if kvmppc_core_vcpu_create_pr() returns an error then this means that kvmppc_mmu_init() was either not called or failed, in which case kvmppc_mmu_destroy() should not be called. Drop the line in the error path of kvm_arch_vcpu_create(). Fixes: ff030fdf55 ("KVM: PPC: Move kvm_vcpu_init() invocation to common code") Signed-off-by: Greg Kurz <groug@kaod.org> Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/158455341029.178873.15248663726399374882.stgit@bahia.lan		2020-03-20 13:39:10 +11:00
..
boot	Kbuild updates for v5.6 (2nd)	2020-02-09 16:05:50 -08:00
configs	virtio: fixes, cleanups	2020-02-07 12:26:34 -08:00
crypto
include	powerpc/32s: Fix DSI and ISI exceptions for CONFIG_VMAP_STACK	2020-02-18 21:31:11 +11:00
kernel	powerpc: fix hardware PMU exception bug on PowerVM compatibility mode systems	2020-02-28 10:09:33 +11:00
kexec
kvm	KVM: PPC: Fix kernel crash with PR KVM	2020-03-20 13:39:10 +11:00
lib
math-emu
mm	powerpc/kasan: Fix shadow memory protection with CONFIG_KASAN_VMALLOC	2020-03-13 21:10:37 +11:00
net
oprofile	powerpc updates for 5.6	2020-02-04 13:06:46 +00:00
perf	powerpc/8xx: Use alternative scratch registers in DTLB miss handler	2020-01-27 22:36:16 +11:00
platforms	ARM: SoC-related driver updates	2020-02-08 14:04:19 -08:00
purgatory
sysdev	powerpc updates for 5.6	2020-02-04 13:06:46 +00:00
tools	powerpc: Do not consider weak unresolved symbol relocations as bad	2020-01-31 20:17:22 +11:00
xmon	powerpc/xmon: Fix whitespace handling in getstring()	2020-02-18 21:31:12 +11:00
Kbuild
Kconfig	powerpc updates for 5.6	2020-02-04 13:06:46 +00:00
Kconfig.debug
Makefile
Makefile.postlink	powerpc: Do not consider weak unresolved symbol relocations as bad	2020-01-31 20:17:22 +11:00