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target/i386: Reject ModRM.reg == 7 early when decoding 0xFE/0xFF (group 4 and 5) instructions #2362

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target/i386: Reject ModRM.reg == 7 early when decoding 0xFE/0xFF (group 4 and 5) instructions #2362

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2 changes: 1 addition & 1 deletion qemu/target/i386/translate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5493,7 +5493,7 @@ static target_ulong disas_insn(DisasContext *s, CPUState *cpu)
mod = (modrm >> 6) & 3;
rm = (modrm & 7) | REX_B(s);
op = (modrm >> 3) & 7;
if (op >= 2 && b == 0xfe) {
if (op == 7 || (op >= 2 && b == 0xfe)) {
goto unknown_op;
}
if (CODE64(s)) {
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19 changes: 19 additions & 0 deletions tests/unit/test_x86.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2656,6 +2656,23 @@ static void test_x86_group_1a(void)
OK(uc_close(uc));
}

static void test_x86_group_5_modrm_reg_7(void)
{
uc_engine *uc;
char code[] = {
0xff, (7 << 3), 0x01, 0x02, 0x03, 0x04
};

uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_64, code, sizeof(code));

uint64_t rax = code_start + code_len + 0x100;
OK(uc_reg_write(uc, UC_X86_REG_RAX, &rax));
uc_assert_err(UC_ERR_INSN_INVALID,
uc_emu_start(uc, code_start, code_start + sizeof(code), 0, 0));

OK(uc_close(uc));
}

static void test_x86_lock_bt_mem(void)
{
uc_engine *uc;
Expand Down Expand Up @@ -2732,6 +2749,7 @@ static void test_x86_lock_btc_reg(void)
OK(uc_close(uc));
}


TEST_LIST = {
{"test_x86_in", test_x86_in},
{"test_x86_out", test_x86_out},
Expand Down Expand Up @@ -2810,6 +2828,7 @@ TEST_LIST = {
{"test_x86_aaa_flags", test_x86_aaa_flags},
{"test_x86_aas_flags", test_x86_aas_flags},
{"test_x86_group_1a", test_x86_group_1a},
{"test_x86_group_5_modrm_reg_7", test_x86_group_5_modrm_reg_7},
{"test_x86_lock_bt_mem", test_x86_lock_bt_mem},
{"test_x86_lock_bt_reg", test_x86_lock_bt_reg},
{"test_x86_lock_btc_mem", test_x86_lock_btc_mem},
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