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Commit 1e47ab3d authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Greg Kroah-Hartman
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x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting 



commit 44a3918c8245ab10c6c9719dd12e7a8d291980d8 upstream.

With unprivileged eBPF enabled, eIBRS (without retpoline) is vulnerable
to Spectre v2 BHB-based attacks.

When both are enabled, print a warning message and report it in the
'spectre_v2' sysfs vulnerabilities file.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
[fllinden@amazon.com: backported to 5.4]
Signed-off-by: default avatarFrank van der Linden <fllinden@amazon.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 327a4da9

arch/x86/kernel/cpu/bugs.c

+29 −6
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 
#include <asm/intel-family.h>

#include <asm/e820/api.h>

#include <asm/hypervisor.h>

#include <linux/bpf.h>



#include "cpu.h"
@@ -607,6 +608,16 @@ static inline const char *spectre_v2_module_string(void) 
static inline const char *spectre_v2_module_string(void) { return ""; }

#endif



#define SPECTRE_V2_EIBRS_EBPF_MSG "WARNING: Unprivileged eBPF is enabled with eIBRS on, data leaks possible via Spectre v2 BHB attacks!\n"



#ifdef CONFIG_BPF_SYSCALL

void unpriv_ebpf_notify(int new_state)

{

	if (spectre_v2_enabled == SPECTRE_V2_EIBRS && !new_state)

		pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);

}

#endif



static inline bool match_option(const char *arg, int arglen, const char *opt)

{

	int len = strlen(opt);
@@ -951,6 +962,9 @@ static void __init spectre_v2_select_mitigation(void) 
		break;

	}



	if (mode == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())

		pr_err(SPECTRE_V2_EIBRS_EBPF_MSG);



	if (spectre_v2_in_eibrs_mode(mode)) {

		/* Force it so VMEXIT will restore correctly */

		x86_spec_ctrl_base |= SPEC_CTRL_IBRS;
@@ -1698,6 +1712,20 @@ static char *ibpb_state(void) 
	return "";

}



static ssize_t spectre_v2_show_state(char *buf)

{

	if (spectre_v2_enabled == SPECTRE_V2_EIBRS && unprivileged_ebpf_enabled())

		return sprintf(buf, "Vulnerable: Unprivileged eBPF enabled\n");



	return sprintf(buf, "%s%s%s%s%s%s\n",

		       spectre_v2_strings[spectre_v2_enabled],

		       ibpb_state(),

		       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",

		       stibp_state(),

		       boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",

		       spectre_v2_module_string());

}



static ssize_t srbds_show_state(char *buf)

{

	return sprintf(buf, "%s\n", srbds_strings[srbds_mitigation]);
@@ -1723,12 +1751,7 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr 
		return sprintf(buf, "%s\n", spectre_v1_strings[spectre_v1_mitigation]);



	case X86_BUG_SPECTRE_V2:

		return sprintf(buf, "%s%s%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],

			       ibpb_state(),

			       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",

			       stibp_state(),

			       boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",

			       spectre_v2_module_string());

		return spectre_v2_show_state(buf);



	case X86_BUG_SPEC_STORE_BYPASS:

		return sprintf(buf, "%s\n", ssb_strings[ssb_mode]);

include/linux/bpf.h

+12 −0
Original line number Diff line number Diff line
@@ -751,6 +751,12 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr, 
int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,

				     const union bpf_attr *kattr,

				     union bpf_attr __user *uattr);



static inline bool unprivileged_ebpf_enabled(void)

{

	return !sysctl_unprivileged_bpf_disabled;

}



#else /* !CONFIG_BPF_SYSCALL */

static inline struct bpf_prog *bpf_prog_get(u32 ufd)

{
@@ -881,6 +887,12 @@ static inline int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog, 
{

	return -ENOTSUPP;

}



static inline bool unprivileged_ebpf_enabled(void)

{

	return false;

}



#endif /* CONFIG_BPF_SYSCALL */



static inline struct bpf_prog *bpf_prog_get_type(u32 ufd,

kernel/sysctl.c

+8 −0
Original line number Diff line number Diff line
@@ -251,6 +251,11 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write, 
#endif



#ifdef CONFIG_BPF_SYSCALL



void __weak unpriv_ebpf_notify(int new_state)

{

}



static int bpf_unpriv_handler(struct ctl_table *table, int write,

                             void *buffer, size_t *lenp, loff_t *ppos)

{
@@ -268,6 +273,9 @@ static int bpf_unpriv_handler(struct ctl_table *table, int write, 
			return -EPERM;

		*(int *)table->data = unpriv_enable;

	}



	unpriv_ebpf_notify(unpriv_enable);



	return ret;

}

#endif