In the LoongArch BPF JIT code, the branch offset represents the number of instructions. An offset of 1 means the target of the "beq" is the current PC plus 1 instruction (PC + 4 bytes). This matches the exact same path as the sequential non-branch execution, the "or" instruction is always executed for the cast_user JIT arm in build_insn(). If the pointer is not NULL, there is no side effect. But if the pointer is NULL, it is incorrectly combined with the base address and turns into a non-zero address, meaning a zero arena offset no longer casts to NULL. Fix this by changing the branch offset from 1 to 2, which properly skips the "or" instruction and jumps directly to the "move_reg" instruction if the pointer is NULL, ensuring the destination register is safely cleared to 0. Fixes: 4fdb5dd8aeba ("LoongArch: BPF: Implement bpf_addr_space_cast instruction") Cc: stable@vger.kernel.org Signed-off-by: Tiezhu Yang --- v2: Update the commit message, no code changes. arch/loongarch/net/bpf_jit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c index 1eb588e443c9..4da278900938 100644 --- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -717,7 +717,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx, bool ext move_reg(ctx, t1, src); emit_zext_32(ctx, t1, true); move_imm(ctx, dst, (ctx->user_vm_start >> 32) << 32, false); - emit_insn(ctx, beq, t1, LOONGARCH_GPR_ZERO, 1); + emit_insn(ctx, beq, t1, LOONGARCH_GPR_ZERO, 2); emit_insn(ctx, or, t1, dst, t1); move_reg(ctx, dst, t1); break; -- 2.42.0