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x86/sev-es: Use new for_each_insn_prefix() macro to loop over prefixes bytes

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Since insn.prefixes.nbytes can be bigger than the size of
insn.prefixes.bytes[] when a prefix is repeated, the proper
check must be:

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

instead of using insn.prefixes.nbytes. Use the new
for_each_insn_prefix() macro which does it correctly.

Debugged by Kees Cook <keescook@chromium.org>.

 [ bp: Massage commit message. ]

Fixes: 25189d08e5 ("x86/sev-es: Add support for handling IOIO exceptions")
Reported-by: syzbot+9b64b619f10f19d19a7c@syzkaller.appspotmail.com
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/160697106089.3146288.2052422845039649176.stgit@devnote2
This commit is contained in:
Masami Hiramatsu 2020-12-03 13:51:01 +09:00 committed by Borislav Petkov
parent 12cb908a11
commit 84da009f06
1 changed files with 2 additions and 3 deletions
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5
arch/x86/boot/compressed/sev-es.c
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@ -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;
}