Commit adad10b3 authored by James Morse's avatar James Morse Committed by Zheng Zengkai
Browse files

arm64: proton-pack: Report Spectre-BHB vulnerabilities as part of Spectre-v2 

stable inclusion
from stable-v5.10.105
commit 13a807a0a080383ceab6c40e53c0228108423e51
category: bugfix
bugzilla: 186460 https://gitee.com/src-openeuler/kernel/issues/I53MHA
CVE: CVE-2022-23960

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=13a807a0a080



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

commit dee435be upstream.

Speculation attacks against some high-performance processors can
make use of branch history to influence future speculation as part of
a spectre-v2 attack. This is not mitigated by CSV2, meaning CPUs that
previously reported 'Not affected' are now moderately mitigated by CSV2.

Update the value in /sys/devices/system/cpu/vulnerabilities/spectre_v2
to also show the state of the BHB mitigation.

Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarChen Jiahao <chenjiahao16@huawei.com>
Reviewed-by: default avatarLiao Chang <liaochang1@huawei.com>
Signed-off-by: default avatarZheng Zengkai <zhengzengkai@huawei.com>
parent 2e56dc8b

arch/arm64/include/asm/spectre.h

+2 −0
Original line number Diff line number Diff line
@@ -29,4 +29,6 @@ bool has_spectre_v4(const struct arm64_cpu_capabilities *cap, int scope); 
void spectre_v4_enable_mitigation(const struct arm64_cpu_capabilities *__unused);

void spectre_v4_enable_task_mitigation(struct task_struct *tsk);



enum mitigation_state arm64_get_spectre_bhb_state(void);



#endif	/* __ASM_SPECTRE_H */

arch/arm64/kernel/proton-pack.c

+34 −2
Original line number Diff line number Diff line
@@ -95,14 +95,39 @@ static bool spectre_v2_mitigations_off(void) 
	return ret;

}



static const char *get_bhb_affected_string(enum mitigation_state bhb_state)

{

	switch (bhb_state) {

	case SPECTRE_UNAFFECTED:

		return "";

	default:

	case SPECTRE_VULNERABLE:

		return ", but not BHB";

	case SPECTRE_MITIGATED:

		return ", BHB";

	}

}



ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr,

			    char *buf)

{

	enum mitigation_state bhb_state = arm64_get_spectre_bhb_state();

	const char *bhb_str = get_bhb_affected_string(bhb_state);

	const char *v2_str = "Branch predictor hardening";



	switch (spectre_v2_state) {

	case SPECTRE_UNAFFECTED:

		if (bhb_state == SPECTRE_UNAFFECTED)

			return sprintf(buf, "Not affected\n");



		/*

		 * Platforms affected by Spectre-BHB can't report

		 * "Not affected" for Spectre-v2.

		 */

		v2_str = "CSV2";

		fallthrough;

	case SPECTRE_MITIGATED:

		return sprintf(buf, "Mitigation: Branch predictor hardening\n");

		return sprintf(buf, "Mitigation: %s%s\n", v2_str, bhb_str);

	case SPECTRE_VULNERABLE:

		fallthrough;

	default:
@@ -788,3 +813,10 @@ int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which) 
		return -ENODEV;

	}

}



static enum mitigation_state spectre_bhb_state;



enum mitigation_state arm64_get_spectre_bhb_state(void)

{

	return spectre_bhb_state;

}