[PATCH v2 3/3] x86/sev-es: Fix not using prefixes.nbytes for loop over prefixes.bytes

Masami Hiramatsu
2020-12-03T04:52:10Z

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 i < 4 and insn.prefixes.bytes[i] != 0 instead
of insn.prefixes.nbytes.

Fixes: 25189d08e516 ("x86/sev-es: Add support for handling IOIO exceptions")
Reported-by: syzbot+9b64b619f10f19d19a7c@syzkaller.appspotmail.com
Debugged-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/boot/compressed/sev-es.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c
index 954cb2702e23..27826c265aab 100644
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -32,13 +32,12 @@ struct ghcb *boot_ghcb;
*/
static bool insn_has_rep_prefix(struct insn *insn)
{
+ insn_byte_t p;
int i;

insn_get_prefixes(insn);

- for (i = 0; i < insn->prefixes.nbytes; i++) {
- insn_byte_t p = insn->prefixes.bytes[i];
-
+ for_each_insn_prefix(insn, i, p) {
if (p == 0xf2 || p == 0xf3)
return true;
}