arm64: fix out-of-range error when adapting for ARM64_SPECTRE_BHB

hulk inclusion
category: bugfix
bugzilla: 186460, https://gitee.com/src-openeuler/kernel/issues/I53MHA
CVE: CVE-2022-23960

--------------------------------

In cpufeature.c, when num is set to ARM64_SPECTRE_BHB, it should
not be passed to cpu_hwcap_keys, otherwise the out-of-range error
would happen as below:

UBSAN: Undefined behaviour in arch/arm64/kernel/cpufeature.c:1742:3
index 40 is out of range for type 'static_key_false [39]'
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.19.90+ #1
Call trace:
dump_backtrace+0x0/0x390
show_stack+0x24/0x30
dump_stack+0x130/0x188
ubsan_epilogue+0x14/0xa4
__ubsan_handle_out_of_bounds+0x144/0x184
__enable_cpu_capabilities+0x158/0x1d4
setup_cpu_features+0x34/0xc8
smp_cpus_done+0x44/0x13c
smp_init+0x188/0x1a4
kernel_init_freeable+0x454/0x974
kernel_init+0x18/0x150
ret_from_fork+0x10/0x18

Because KABI cpu_hwcap_keys is consistent and defined with length
ARM64_NCAPS, which is smaller than ARM64_SPECTRE_BHB.

Fixes: 2df7cf89 ("arm64: fix extra cpucaps setup problem")
Signed-off-by: NChen Jiahao <chenjiahao16@huawei.com>
Reviewed-by: NLiao Chang <liaochang1@huawei.com>
Reviewed-by: NZhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

arch/arm64/kernel/cpufeature.c

@@ -1732,8 +1732,10 @@ __enable_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
 	for (; caps->matches; caps++) {
 		unsigned int num = caps->capability;
 
-		if (num == ARM64_SPECTRE_BHB)
+		if (num == ARM64_SPECTRE_BHB) {
 			set_cap_spectre_bhb = true;
+			continue;
+		}
 
 		if (!(caps->type & scope_mask) || !cpus_have_cap(num))
 			continue;