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[213.115.136.2]) by smtp.gmail.com with ESMTPSA id c8sm1989732ejp.124.2021.08.09.02.35.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Aug 2021 02:35:15 -0700 (PDT) From: Johan Almbladh To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org Cc: kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, illusionist.neo@gmail.com, zlim.lnx@gmail.com, paulburton@kernel.org, naveen.n.rao@linux.ibm.com, sandipan@linux.ibm.com, luke.r.nels@gmail.com, bjorn@kernel.org, iii@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, davem@davemloft.net, udknight@gmail.com, Johan Almbladh Subject: [PATCH bpf-next 6/7] mips: bpf: Fix off-by-one in tail call count limiting Date: Mon, 9 Aug 2021 11:34:36 +0200 Message-Id: <20210809093437.876558-7-johan.almbladh@anyfinetworks.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210809093437.876558-1-johan.almbladh@anyfinetworks.com> References: <20210809093437.876558-1-johan.almbladh@anyfinetworks.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Before, the eBPF JIT allowed up to MAX_TAIL_CALL_CNT + 1 tail calls. Now, precisely MAX_TAIL_CALL_CNT is allowed, which is in line with the behaviour of the interpreter. Verified with the test_bpf test suite on qemu-system-mips64. Signed-off-by: Johan Almbladh --- arch/mips/net/ebpf_jit.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c index 3a73e9375712..a93121d71c80 100644 --- a/arch/mips/net/ebpf_jit.c +++ b/arch/mips/net/ebpf_jit.c @@ -617,14 +617,14 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx) b_off = b_imm(this_idx + 1, ctx); emit_instr(ctx, bne, MIPS_R_AT, MIPS_R_ZERO, b_off); /* - * if (TCC-- < 0) + * if (TCC-- <= 0) * goto out; */ /* Delay slot */ tcc_reg = (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4; emit_instr(ctx, daddiu, MIPS_R_T5, tcc_reg, -1); b_off = b_imm(this_idx + 1, ctx); - emit_instr(ctx, bltz, tcc_reg, b_off); + emit_instr(ctx, blez, tcc_reg, b_off); /* * prog = array->ptrs[index]; * if (prog == NULL)