KVM: x86: emulator: em_sysexit should update ctxt->mode

commit 5015bb89b58225f97df6ac44383e7e8c8662c8c9 upstream.

SYSEXIT is one of the instructions that can change the
processor mode, thus ctxt->mode should be updated after it.

Note that this is likely a benign bug, because the only problematic
mode change is from 32 bit to 64 bit which can lead to truncation of RIP,
and it is not possible to do with sysexit,
since sysexit running in 32 bit mode will be limited to 32 bit version.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20221025124741.228045-11-mlevitsk@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 16e24085fc8b19fd62fc96909d4f3c77f45e8971..16ab6ab32ae55cad4c369775b1c2465342950034 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2881,6 +2881,7 @@ static int em_sysexit(struct x86_emulate_ctxt *ctxt)
        ops->set_segment(ctxt, ss_sel, &ss, 0, VCPU_SREG_SS);
 
        ctxt->_eip = rdx;
+       ctxt->mode = usermode;
        *reg_write(ctxt, VCPU_REGS_RSP) = rcx;
 
        return X86EMUL_CONTINUE;