From: James Morse <james.morse@xxxxxxx> commit 58c9a5060cb7cd529d49c93954cdafe81c1d642a upstream. The mitigations for Spectre-BHB are only applied when an exception is taken from user-space. The mitigation status is reported via the spectre_v2 sysfs vulnerabilities file. When unprivileged eBPF is enabled the mitigation in the exception vectors can be avoided by an eBPF program. When unprivileged eBPF is enabled, print a warning and report vulnerable via the sysfs vulnerabilities file. Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: James Morse <james.morse@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/proton-pack.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) --- a/arch/arm64/kernel/proton-pack.c +++ b/arch/arm64/kernel/proton-pack.c @@ -18,6 +18,7 @@ */ #include <linux/arm-smccc.h> +#include <linux/bpf.h> #include <linux/cpu.h> #include <linux/device.h> #include <linux/nospec.h> @@ -111,6 +112,15 @@ static const char *get_bhb_affected_stri } } +static bool _unprivileged_ebpf_enabled(void) +{ +#ifdef CONFIG_BPF_SYSCALL + return !sysctl_unprivileged_bpf_disabled; +#else + return false; +#endif +} + ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf) { @@ -130,6 +140,9 @@ ssize_t cpu_show_spectre_v2(struct devic v2_str = "CSV2"; fallthrough; case SPECTRE_MITIGATED: + if (bhb_state == SPECTRE_MITIGATED && _unprivileged_ebpf_enabled()) + return sprintf(buf, "Vulnerable: Unprivileged eBPF enabled\n"); + return sprintf(buf, "Mitigation: %s%s\n", v2_str, bhb_str); case SPECTRE_VULNERABLE: fallthrough; @@ -1125,3 +1138,16 @@ void __init spectre_bhb_patch_clearbhb(s *updptr++ = cpu_to_le32(aarch64_insn_gen_nop()); *updptr++ = cpu_to_le32(aarch64_insn_gen_nop()); } + +#ifdef CONFIG_BPF_SYSCALL +#define EBPF_WARN "Unprivileged eBPF is enabled, data leaks possible via Spectre v2 BHB attacks!\n" +void unpriv_ebpf_notify(int new_state) +{ + if (spectre_v2_state == SPECTRE_VULNERABLE || + spectre_bhb_state != SPECTRE_MITIGATED) + return; + + if (!new_state) + pr_err("WARNING: %s", EBPF_WARN); +} +#endif Patches currently in stable-queue which might be from james.morse@xxxxxxx are queue-5.16/arm64-entry-add-macro-for-reading-symbol-addresses-from-the-trampoline.patch queue-5.16/arm64-use-the-clearbhb-instruction-in-mitigations.patch queue-5.16/arm64-add-percpu-vectors-for-el1.patch queue-5.16/arm64-entry-free-up-another-register-on-kpti-s-tramp_exit-path.patch queue-5.16/arm64-entry-don-t-assume-tramp_vectors-is-the-start-of-the-vectors.patch queue-5.16/arm64-entry-make-the-trampoline-cleanup-optional.patch queue-5.16/arm64-proton-pack-include-unprivileged-ebpf-status-in-spectre-v2-mitigation-reporting.patch queue-5.16/arm64-entry-add-non-kpti-__bp_harden_el1_vectors-for-mitigations.patch queue-5.16/arm64-add-id_aa64isar2_el1-sys-register.patch queue-5.16/kvm-arm64-allow-smccc_arch_workaround_3-to-be-discovered-and-migrated.patch queue-5.16/arm64-spectre-rename-spectre_v4_patch_fw_mitigation_conduit.patch queue-5.16/arm64-entry-move-trampoline-macros-out-of-ifdef-d-section.patch queue-5.16/arm64-entry-allow-tramp_alias-to-access-symbols-after-the-4k-boundary.patch queue-5.16/arm64-entry-move-the-trampoline-data-page-before-the-text-page.patch queue-5.16/arm64-entry.s-add-ventry-overflow-sanity-checks.patch queue-5.16/arm64-entry-add-vectors-that-have-the-bhb-mitigation-sequences.patch queue-5.16/arm64-mitigate-spectre-style-branch-history-side-channels.patch queue-5.16/arm64-entry-allow-the-trampoline-text-to-occupy-multiple-pages.patch queue-5.16/arm64-proton-pack-report-spectre-bhb-vulnerabilities-as-part-of-spectre-v2.patch queue-5.16/kvm-arm64-allow-indirect-vectors-to-be-used-without-spectre_v3a.patch queue-5.16/arm64-entry-make-the-kpti-trampoline-s-kpti-sequence-optional.patch