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Greg Kurz b2fa4f9088 KVM: PPC: Book3S PR: 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: Paul Mackerras <paulus@ozlabs.org>
2020-03-19 16:39:52 +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 crypto: remove CRYPTO_TFM_RES_BAD_KEY_LEN 2020-01-09 11:30:53 +08:00
include KVM: PPC: Book3S HV: Treat TM-related invalid form instructions on P9 like the valid ones 2020-03-19 16:39:52 +11:00
kernel powerpc: Fix CONFIG_TRACE_IRQFLAGS with CONFIG_VMAP_STACK 2020-02-08 21:49:06 +11:00
kexec powerpc: Avoid clang warnings around setjmp and longjmp 2019-11-25 21:45:43 +11:00
kvm KVM: PPC: Book3S PR: Fix kernel crash with PR KVM 2020-03-19 16:39:52 +11:00
lib powerpc: Fix __clear_user() with KUAP enabled 2019-12-16 23:19:44 +11:00
math-emu
mm powerpc updates for 5.6 2020-02-04 13:06:46 +00:00
net treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
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 compile error in print_insn* functions 2020-01-26 00:11:35 +11:00
Kbuild powerpc/kexec: Move kexec files into a dedicated subdir. 2019-11-21 15:41:34 +11:00
Kconfig powerpc updates for 5.6 2020-02-04 13:06:46 +00:00
Kconfig.debug powerpc/ptdump: Only enable PPC_CHECK_WX with STRICT_KERNEL_RWX 2020-01-23 21:31:13 +11:00
Makefile powerpc: Don't add -mabi= flags when building with Clang 2019-11-25 21:45:43 +11:00
Makefile.postlink powerpc: Do not consider weak unresolved symbol relocations as bad 2020-01-31 20:17:22 +11:00