arm64: bpf: Only mitigate cBPF programs loaded by unprivileged users

commit f300769ead032513a68e4a02e806393402e626f8 upstream.

Support for eBPF programs loaded by unprivileged users is typically
disabled. This means only cBPF programs need to be mitigated for BHB.

In addition, only mitigate cBPF programs that were loaded by an
unprivileged user. Privileged users can also load the same program
via eBPF, making the mitigation pointless.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 3eca30605b8a65a68ca1abebe28a5cc6c9f19d4a..09b70a9b5c393a9c6fb4252bfb203e97d9e50423 100644 (file)
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -666,6 +666,9 @@ static void __maybe_unused build_bhb_mitigation(struct jit_ctx *ctx)
            arm64_get_spectre_v2_state() == SPECTRE_VULNERABLE)
                return;
 
+       if (capable(CAP_SYS_ADMIN))
+               return;
+
        if (supports_clearbhb(SCOPE_SYSTEM)) {
                emit(aarch64_insn_gen_hint(AARCH64_INSN_HINT_CLEARBHB), ctx);
                return;