From: Yonghong Song <yonghong.song@linux.dev>
Date: Wed, 13 May 2026 04:50:59 +0000 (-0700)
Subject: bpf: Enable r11 based insns
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9fae4cba3bfd583198afe15ed4b4433eafafd11c;p=thirdparty%2Flinux.git

bpf: Enable r11 based insns

BPF_REG_PARAMS (r11) is used for stack argument accesses and
the following are only insns with r11 presence:
    - load incoming stack arg
    - store register to outgoing stack arg
    - store immediate to outgoing stack arg

The detailed insn format can be found in is_stack_arg_ldx/st/stx()
helpers. After this patch, stack arg ldx/st/stx insns become valid
for kernel and these insns can be properly checked by verifier.

The LLVM compiler [1] implemented the above BPF_REG_PARAMS insns.

  [1] https://github.com/llvm/llvm-project/pull/189060

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260513045059.2391192-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ebd13661933ea..b0d3c2d179e4b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18006,11 +18006,12 @@ static int check_and_resolve_insns(struct bpf_verifier_env *env)
 		return err;
 
 	for (i = 0; i < insn_cnt; i++, insn++) {
-		if (insn->dst_reg >= MAX_BPF_REG) {
+		if (insn->dst_reg >= MAX_BPF_REG &&
+		    !is_stack_arg_st(insn) && !is_stack_arg_stx(insn)) {
 			verbose(env, "R%d is invalid\n", insn->dst_reg);
 			return -EINVAL;
 		}
-		if (insn->src_reg >= MAX_BPF_REG) {
+		if (insn->src_reg >= MAX_BPF_REG && !is_stack_arg_ldx(insn)) {
 			verbose(env, "R%d is invalid\n", insn->src_reg);
 			return -EINVAL;
 		}