From: Russell King (Oracle) rmk+kernel@armlinux.org.uk
commit 25875aa71dfefd1959f07e626c4d285b88b27ac2 upstream.
The mitigations for Spectre-BHB are only applied when an exception is taken, but when unprivileged BPF is enabled, userspace can load BPF programs that can be used to exploit the problem.
When unprivileged BPF is enabled, report the vulnerable status via the spectre_v2 sysfs file.
Signed-off-by: Russell King (Oracle) rmk+kernel@armlinux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm/kernel/spectre.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
--- a/arch/arm/kernel/spectre.c +++ b/arch/arm/kernel/spectre.c @@ -1,9 +1,19 @@ // SPDX-License-Identifier: GPL-2.0-only +#include <linux/bpf.h> #include <linux/cpu.h> #include <linux/device.h>
#include <asm/spectre.h>
+static bool _unprivileged_ebpf_enabled(void) +{ +#ifdef CONFIG_BPF_SYSCALL + return !sysctl_unprivileged_bpf_disabled; +#else + return false +#endif +} + ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf) { @@ -31,6 +41,9 @@ ssize_t cpu_show_spectre_v2(struct devic if (spectre_v2_state != SPECTRE_MITIGATED) return sprintf(buf, "%s\n", "Vulnerable");
+ if (_unprivileged_ebpf_enabled()) + return sprintf(buf, "Vulnerable: Unprivileged eBPF enabled\n"); + switch (spectre_v2_methods) { case SPECTRE_V2_METHOD_BPIALL: method = "Branch predictor hardening";