From: "Borislav Petkov (AMD)" bp@alien8.de
stable inclusion from stable-v5.10.192 commit 69712baf249570a1419e75dc1a103a44e375b2cd category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I7WY4J CVE: CVE-2023-20588
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit f58d6fbcb7c848b7f2469be339bc571f2e9d245b upstream.
Initially, it was thought that doing an innocuous division in the #DE handler would take care to prevent any leaking of old data from the divider but by the time the fault is raised, the speculation has already advanced too far and such data could already have been used by younger operations.
Therefore, do the innocuous division on every exit to userspace so that userspace doesn't see any potentially old data from integer divisions in kernel space.
Do the same before VMRUN too, to protect host data from leaking into the guest too.
Fixes: 77245f1c3c64 ("x86/CPU/AMD: Do not leak quotient data after a division by 0") Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Cc: stable@kernel.org Link: https://lore.kernel.org/r/20230811213824.10025-1-bp@alien8.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Conflicts: arch/x86/entry/common.c arch/x86/kernel/cpu/amd.c arch/x86/kvm/svm.c
Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- arch/x86/entry/common.c | 1 + arch/x86/kernel/cpu/amd.c | 1 + arch/x86/kvm/svm.c | 1 + 3 files changed, 3 insertions(+)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c index 0723098a3961..d3944912cc81 100644 --- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -215,6 +215,7 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs) user_enter_irqoff();
mds_user_clear_cpu_buffers(); + amd_clear_divider(); }
#define SYSCALL_EXIT_WORK_FLAGS \ diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 3abcc656d27f..002aa4bd35cf 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -1252,3 +1252,4 @@ void amd_clear_divider(void) asm volatile(ALTERNATIVE("", "div %2\n\t", X86_BUG_DIV0) :: "a" (0), "d" (0), "r" (1)); } +EXPORT_SYMBOL_GPL(amd_clear_divider); diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index b209f7f8eb5b..76fe2bf07016 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -5536,6 +5536,7 @@ static void svm_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t gva)
static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu) { + amd_clear_divider(); }
static inline void sync_cr8_to_lapic(struct kvm_vcpu *vcpu)