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[213.115.136.2]) by smtp.gmail.com with ESMTPSA id c8sm1989732ejp.124.2021.08.09.02.35.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Aug 2021 02:35:08 -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 1/7] arm: bpf: Fix off-by-one in tail call count limiting Date: Mon, 9 Aug 2021 11:34:31 +0200 Message-Id: <20210809093437.876558-2-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 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-arm. Signed-off-by: Johan Almbladh --- arch/arm/net/bpf_jit_32.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index a951276f0547..200ae9d24205 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -1180,12 +1180,12 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) /* tmp2[0] = array, tmp2[1] = index */ - /* if (tail_call_cnt > MAX_TAIL_CALL_CNT) + /* if (tail_call_cnt >= MAX_TAIL_CALL_CNT) * goto out; * tail_call_cnt++; */ - lo = (u32)MAX_TAIL_CALL_CNT; - hi = (u32)((u64)MAX_TAIL_CALL_CNT >> 32); + lo = (u32)(MAX_TAIL_CALL_CNT - 1); + hi = (u32)((u64)(MAX_TAIL_CALL_CNT - 1) >> 32); tc = arm_bpf_get_reg64(tcc, tmp, ctx); emit(ARM_CMP_I(tc[0], hi), ctx); _emit(ARM_COND_EQ, ARM_CMP_I(tc[1], lo), ctx);