kvm: x86: use correct privilege level for sgdt/sidt/fxsave/fxrstor access
commit 3c9fa24ca7c9c47605672916491f79e8ccacb9e6 upstream.
The functions that were used in the emulation of fxrstor, fxsave, sgdt and
sidt were originally meant for task switching, and as such they did not
check privilege levels. This is very bad when the same functions are used
in the emulation of unprivileged instructions. This is CVE-2018-10853.
The obvious fix is to add a new argument to ops->read_std and ops->write_std,
which decides whether the access is a "system" access or should use the
processor's CPL.
Fixes: 129a72a0d3c8 ("KVM: x86: Introduce segmented_write_std", 2017-01-12)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index fc3c7e4..ae357d0 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -105,11 +105,12 @@
* @addr: [IN ] Linear address from which to read.
* @val: [OUT] Value read from memory, zero-extended to 'u_long'.
* @bytes: [IN ] Number of bytes to read from memory.
+ * @system:[IN ] Whether the access is forced to be at CPL0.
*/
int (*read_std)(struct x86_emulate_ctxt *ctxt,
unsigned long addr, void *val,
unsigned int bytes,
- struct x86_exception *fault);
+ struct x86_exception *fault, bool system);
/*
* read_phys: Read bytes of standard (non-emulated/special) memory.
@@ -127,10 +128,11 @@
* @addr: [IN ] Linear address to which to write.
* @val: [OUT] Value write to memory, zero-extended to 'u_long'.
* @bytes: [IN ] Number of bytes to write to memory.
+ * @system:[IN ] Whether the access is forced to be at CPL0.
*/
int (*write_std)(struct x86_emulate_ctxt *ctxt,
unsigned long addr, void *val, unsigned int bytes,
- struct x86_exception *fault);
+ struct x86_exception *fault, bool system);
/*
* fetch: Read bytes of standard (non-emulated/special) memory.
* Used for instruction fetch.