[PATCH 1/3] x86/sev-es: Fix not using prefixes.nbytes for loop over prefixes.bytes

[Masami Hiramatsu]

Since the insn.prefixes.nbytes can be bigger than the size of
insn.prefixes.bytes[] when a same prefix is repeated, we have to
check whether the insn.prefixes.bytes[i] != 0 and i < 4 instead
of insn.prefixes.nbytes.

Fixes: 25189d08e516 ("x86/sev-es: Add support for handling IOIO exceptions")
Reported-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 arch/x86/boot/compressed/sev-es.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c
index 954cb2702e23..6a7a3027c9ac 100644
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -36,7 +36,7 @@ static bool insn_has_rep_prefix(struct insn *insn)
 
 	insn_get_prefixes(insn);
 
-	for (i = 0; i < insn->prefixes.nbytes; i++) {
+	for (i = 0; insn->prefixes.bytes[i] && i < 4; i++) {
 		insn_byte_t p = insn->prefixes.bytes[i];
 
 		if (p == 0xf2 || p == 0xf3)