6.12-stable review patch. If anyone has any objections, please let me know.
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From: Hengqi Chen hengqi.chen@gmail.com
commit 60f3caff1492e5b8616b9578c4bedb5c0a88ed14 upstream.
The verifier test `calls: div by 0 in subprog` triggers a panic at the ld.bu instruction. The ld.bu insn is trying to load byte from memory address returned by the subprog. The subprog actually set the correct address at the a5 register (dedicated register for BPF return values). But at commit 73c359d1d356 ("LoongArch: BPF: Sign-extend return values") we also sign extended a5 to the a0 register (return value in LoongArch). For function call insn, we later propagate the a0 register back to a5 register. This is right for native calls but wrong for bpf2bpf calls which expect zero-extended return value in a5 register. So only move a0 to a5 for native calls (i.e. non-BPF_PSEUDO_CALL).
Cc: stable@vger.kernel.org Fixes: 73c359d1d356 ("LoongArch: BPF: Sign-extend return values") Signed-off-by: Hengqi Chen hengqi.chen@gmail.com Signed-off-by: Huacai Chen chenhuacai@loongson.cn Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/loongarch/net/bpf_jit.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/arch/loongarch/net/bpf_jit.c +++ b/arch/loongarch/net/bpf_jit.c @@ -907,7 +907,10 @@ static int build_insn(const struct bpf_i
move_addr(ctx, t1, func_addr); emit_insn(ctx, jirl, LOONGARCH_GPR_RA, t1, 0); - move_reg(ctx, regmap[BPF_REG_0], LOONGARCH_GPR_A0); + + if (insn->src_reg != BPF_PSEUDO_CALL) + move_reg(ctx, regmap[BPF_REG_0], LOONGARCH_GPR_A0); + break;
/* tail call */