From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
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: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
[fllinden@xxxxxxxxxx: backported to 5.4]
Signed-off-by: Frank van der Linden <fllinden@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/bugs.c | 35 +++++++++++++++++++++++++++++------
include/linux/bpf.h | 12 ++++++++++++
kernel/sysctl.c | 8 ++++++++
3 files changed, 49 insertions(+), 6 deletions(-)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -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_mod
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_mit
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 de
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]);
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -751,6 +751,12 @@ int bpf_prog_test_run_skb(struct bpf_pro
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
{
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,
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -251,6 +251,11 @@ static int sysrq_sysctl_handler(struct c
#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
return -EPERM;
*(int *)table->data = unpriv_enable;
}
+
+ unpriv_ebpf_notify(unpriv_enable);
+
return ret;
}
#endif
