KVM: x86: fix off-by-one in reserved bits check
29ecd6601904 ("KVM: x86: avoid uninitialized variable warning",
2015-09-06) introduced a not-so-subtle problem, which probably
escaped review because it was not part of the patch context.
Before the patch, leaf was always equal to iterator.level. After,
it is equal to iterator.level - 1 in the call to is_shadow_zero_bits_set,
and when is_shadow_zero_bits_set does another "-1" the check on
reserved bits becomes incorrect. Using "iterator.level" in the call
fixes this call trace:
WARNING: CPU: 2 PID: 17000 at arch/x86/kvm/mmu.c:3385 handle_mmio_page_fault.part.93+0x1a/0x20 [kvm]()
Modules linked in: tun sha256_ssse3 sha256_generic drbg binfmt_misc ipv6 vfat fat fuse dm_crypt dm_mod kvm_amd kvm crc32_pclmul aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd fam15h_power amd64_edac_mod k10temp edac_core amdkfd amd_iommu_v2 radeon acpi_cpufreq
[...]
Call Trace:
dump_stack+0x4e/0x84
warn_slowpath_common+0x95/0xe0
warn_slowpath_null+0x1a/0x20
handle_mmio_page_fault.part.93+0x1a/0x20 [kvm]
tdp_page_fault+0x231/0x290 [kvm]
? emulator_pio_in_out+0x6e/0xf0 [kvm]
kvm_mmu_page_fault+0x36/0x240 [kvm]
? svm_set_cr0+0x95/0xc0 [kvm_amd]
pf_interception+0xde/0x1d0 [kvm_amd]
handle_exit+0x181/0xa70 [kvm_amd]
? kvm_arch_vcpu_ioctl_run+0x68b/0x1730 [kvm]
kvm_arch_vcpu_ioctl_run+0x6f6/0x1730 [kvm]
? kvm_arch_vcpu_ioctl_run+0x68b/0x1730 [kvm]
? preempt_count_sub+0x9b/0xf0
? mutex_lock_killable_nested+0x26f/0x490
? preempt_count_sub+0x9b/0xf0
kvm_vcpu_ioctl+0x358/0x710 [kvm]
? __fget+0x5/0x210
? __fget+0x101/0x210
do_vfs_ioctl+0x2f4/0x560
? __fget_light+0x29/0x90
SyS_ioctl+0x4c/0x90
entry_SYSCALL_64_fastpath+0x16/0x73
---[ end trace 37901c8686d84de6 ]---
Reported-by: Borislav Petkov <bp@alien8.de>
Tested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed