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| author | Borislav Petkov (AMD) <bp@alien8.de> | 2023-08-11 23:38:24 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-08-26 13:27:00 +0200 |
| commit | e4679a0342e05a962639a6ec3781f257f417f0ff (patch) | |
| tree | e2d500ab9ff1a7c15dfa9f85acc7cdd731773173 /arch | |
| parent | b41eb316c95c98d16dba2045c4890a3020f0a5bc (diff) | |
| download | linux-e4679a0342e05a962639a6ec3781f257f417f0ff.tar.gz | |
x86/CPU/AMD: Fix the DIV(0) initial fix attempt
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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/entry-common.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/amd.c | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/traps.c | 2 | ||||
| -rw-r--r-- | arch/x86/kvm/svm/svm.c | 2 |
4 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/include/asm/entry-common.h b/arch/x86/include/asm/entry-common.h index 674ed46d3ced..11203a9fe0a8 100644 --- a/arch/x86/include/asm/entry-common.h +++ b/arch/x86/include/asm/entry-common.h @@ -92,6 +92,7 @@ static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs, static __always_inline void arch_exit_to_user_mode(void) { mds_user_clear_cpu_buffers(); + amd_clear_divider(); } #define arch_exit_to_user_mode arch_exit_to_user_mode diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 239b302973d7..f240c978d85e 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -1295,3 +1295,4 @@ void noinstr 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/kernel/traps.c b/arch/x86/kernel/traps.c index 7e8795d8b0f1..c0a5a4f225d9 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -206,8 +206,6 @@ DEFINE_IDTENTRY(exc_divide_error) { do_error_trap(regs, 0, "divide error", X86_TRAP_DE, SIGFPE, FPE_INTDIV, error_get_trap_addr(regs)); - - amd_clear_divider(); } DEFINE_IDTENTRY(exc_overflow) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index fdb6007f2eb8..a96f9a17e8b5 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3947,6 +3947,8 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in guest_state_enter_irqoff(); + amd_clear_divider(); + if (sev_es_guest(vcpu->kvm)) __svm_sev_es_vcpu_run(svm, spec_ctrl_intercepted); else |