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| author | Paolo Bonzini <pbonzini@redhat.com> | 2017-06-07 15:13:14 +0200 |
|---|---|---|
| committer | Haitao Shan <hshan@google.com> | 2024-04-01 18:44:31 -0700 |
| commit | 91fd654925f712c52e421d9eb6429b7f5fea562c (patch) | |
| tree | 0740119a12d0b25e20b024171e49dddf7f264e06 /arch/x86/kvm/emulate.c | |
| parent | 4343762dc54a8e7fbe04a01db8172da09f3a68e0 (diff) | |
| download | aehd-91fd654925f712c52e421d9eb6429b7f5fea562c.tar.gz | |
KVM: x86: fix singlestepping over syscall
TF is handled a bit differently for syscall and sysret, compared
to the other instructions: TF is checked after the instruction completes,
so that the OS can disable #DB at a syscall by adding TF to FMASK.
When the sysret is executed the #DB is taken "as if" the syscall insn
just completed.
KVM emulates syscall so that it can trap 32-bit syscall on Intel processors.
Fix the behavior, otherwise you could get #DB on a user stack which is not
nice. This does not affect Linux guests, as they use an IST or task gate
for #DB.
This fixes CVE-2017-7518.
Cc: stable@vger.kernel.org
Reported-by: Andy Lutomirski <luto@kernel.org>
Change-Id: I15ecfc775773da50b075ffa3d92b9b57df488eaf
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Diffstat (limited to 'arch/x86/kvm/emulate.c')
| -rwxr-xr-x | arch/x86/kvm/emulate.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 7deb754..3f217f8 100755 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2812,6 +2812,7 @@ static int em_syscall(struct x86_emulate_ctxt *ctxt) ctxt->eflags &= ~(X86_EFLAGS_VM | X86_EFLAGS_IF); } + ctxt->tf = (ctxt->eflags & X86_EFLAGS_TF) != 0; return X86EMUL_CONTINUE; } |