From: Pu Lehui pulehui@huawei.com
[ Upstream commit b54b6003612a376e7be32cbc5c1af3754bbbbb3d ]
For BPF_PSEUDO_FUNC instruction, verifier will refill imm with correct addresses of bpf_calls and then run last pass of JIT. Since the emit_imm of RV64 is variable-length, which will emit appropriate length instructions accorroding to the imm, it may broke ctx->offset, and lead to unpredictable problem, such as inaccurate jump. So let's fix it with fixed-length instructions.
Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Suggested-by: Björn Töpel bjorn@rivosinc.com Signed-off-by: Pu Lehui pulehui@huawei.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: Björn Töpel bjorn@kernel.org Acked-by: Björn Töpel bjorn@kernel.org Link: https://lore.kernel.org/bpf/20221206091410.1584784-1-pulehui@huaweicloud.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/net/bpf_jit_comp64.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 00df3a8f92ac..f2417ac54edd 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -136,6 +136,25 @@ static bool in_auipc_jalr_range(s64 val) val < ((1L << 31) - (1L << 11)); }
+/* Emit fixed-length instructions for address */ +static int emit_addr(u8 rd, u64 addr, bool extra_pass, struct rv_jit_context *ctx) +{ + u64 ip = (u64)(ctx->insns + ctx->ninsns); + s64 off = addr - ip; + s64 upper = (off + (1 << 11)) >> 12; + s64 lower = off & 0xfff; + + if (extra_pass && !in_auipc_jalr_range(off)) { + pr_err("bpf-jit: target offset 0x%llx is out of range\n", off); + return -ERANGE; + } + + emit(rv_auipc(rd, upper), ctx); + emit(rv_addi(rd, rd, lower), ctx); + return 0; +} + +/* Emit variable-length instructions for 32-bit and 64-bit imm */ static void emit_imm(u8 rd, s64 val, struct rv_jit_context *ctx) { /* Note that the immediate from the add is sign-extended, @@ -1050,7 +1069,15 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx, u64 imm64;
imm64 = (u64)insn1.imm << 32 | (u32)imm; - emit_imm(rd, imm64, ctx); + if (bpf_pseudo_func(insn)) { + /* fixed-length insns for extra jit pass */ + ret = emit_addr(rd, imm64, extra_pass, ctx); + if (ret) + return ret; + } else { + emit_imm(rd, imm64, ctx); + } + return 1; }