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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id be17-20020a056512251100b0050bc39bdd43sm696321lfb.211.2023.12.05.15.22.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Dec 2023 15:22:14 -0800 (PST) Message-ID: Subject: Re: [PATCH bpf-next 10/13] bpf: support 'arg:xxx' btf_decl_tag-based hints for global subprog args From: Eduard Zingerman To: Andrii Nakryiko , bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org Cc: kernel-team@meta.com Date: Wed, 06 Dec 2023 01:22:13 +0200 In-Reply-To: <20231204233931.49758-11-andrii@kernel.org> References: <20231204233931.49758-1-andrii@kernel.org> <20231204233931.49758-11-andrii@kernel.org> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=mQGNBGKNNQEBDACwcUNXZOGTzn4rr7Sd18SA5Wv0Wna/ONE0ZwZEx+sIjyGrPOIhR14/DsOr3ZJer9UJ/WAJwbxOBj6E5Y2iF7grehljNbLr/jMjzPJ+hJpfOEAb5xjCB8xIqDoric1WRcCaRB+tDSk7jcsIIiMish0diTK3qTdu4MB6i/sh4aeFs2nifkNi3LdBuk8Xnk+RJHRoKFJ+C+EoSmQPuDQIRaF9N2m4yO0eG36N8jLwvUXnZzGvHkphoQ9ztbRJp58oh6xT7uH62m98OHbsVgzYKvHyBu/IU2ku5kVG9pLrFp25xfD4YdlMMkJH6l+jk+cpY0cvMTS1b6/g+1fyPM+uzD8Wy+9LtZ4PHwLZX+t4ONb/48i5AKq/jSsb5HWdciLuKEwlMyFAihZamZpEj+9n91NLPX4n7XeThXHaEvaeVVl4hfW/1Qsao7l1YjU/NCHuLaDeH4U1P59bagjwo9d1n5/PESeuD4QJFNqW+zkmE4tmyTZ6bPV6T5xdDRHeiITGc00AEQEAAbQkRWR1YXJkIFppbmdlcm1hbiA8ZWRkeXo4N0BnbWFpbC5jb20+iQHUBBMBCgA+FiEEx+6LrjApQyqnXCYELgxleklgRAkFAmKNNQECGwMFCQPCZwAFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AACgkQLgxleklgRAlWZAv/cJ5v3zlEyP0/jMKQBqbVCCHTirPEw+nqxbkeSO6r2FUds0NnGA9a6NPOpBH+qW7a6+n6q3sIbvH7jlss4pzLI7LYlDC6z+egTv7KR5X1xFrY1uR5UGs1beAjnzYeV2hK4yqRUfygsT0Wk5e4FiNBv4+DUZ8r0cNDkO6swJxU55DO21mcteC147+4aDoHZ40R0tsAu+brDGSSoOPpb0RWVsEf9XOBJqWWA+T7mluw nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv iCTce6yYIygHgUAtJcHozAlgRrL0jz44cggBTcoeXp/atckXK546OugZPnl00J3qmm5uWAznU6T5YDv2vCvAMEbz69ib+kHtnOSBvR0Jb86UZZqSb4ATfwMOWe9htGTjKMb0QQOLK0mTcrk/TtymaG+T4Fsos0kgrxqjgfrxxEhYcVNW8v8HISmFGFbqsJmFbVtgk68BcU0wgF8oFxo7u+XYQDdKbI1uQGNBGKNNQEBDADbQIdo8L3sdSWGQtu+LnFqCZoAbYurZCmUjLV3df1b+sg+GJZvVTmMZnzDP/ADufcbjopBBjGTRAY4L76T2niu2EpjclMMM3mtrOc738Kr3+RvPjUupdkZ1ZEZaWpf4cZm+4wH5GUfyu5pmD5WXX2i1r9XaUjeVtebvbuXWmWI1ZDTfOkiz/6Z0GDSeQeEqx2PXYBcepU7S9UNWttDtiZ0+IH4DZcvyKPUcK3tOj4u8GvO3RnOrglERzNCM/WhVdG1+vgU9fXO83TB/PcfAsvxYSie7u792s/I+yA4XKKh82PSTvTzg2/4vEDGpI9yubkfXRkQN28w+HKF5qoRB8/L1ZW/brlXkNzA6SveJhCnH7aOF0Yezl6TfX27w1CW5Xmvfi7X33V/SPvo0tY1THrO1c+bOjt5F+2/K3tvejmXMS/I6URwa8n1e767y5ErFKyXAYRweE9zarEgpNZTuSIGNNAqK+SiLLXt51G7P30TVavIeB6s2lCt1QKt62ccLqUAEQEAAYkBvAQYAQoAJhYhBMfui64wKUMqp1wmBC4MZXpJYEQJBQJijTUBAhsMBQkDwmcAAAoJEC4MZXpJYEQJkRAMAKNvWVwtXm/WxWoiLnXyF2WGXKoDe5+itTLvBmKcV/b1OKZF1s90V7WfSBz712eFAynEzyeezPbwU8QBiTpZcHXwQni3IYKvsh7s t1iq+gsfnXbPz5AnS598ScZI1oP7OrPSFJkt/z4acEbOQDQs8aUqrd46PV jsdqGvKnXZxzylux29UTNby4jTlz9pNJM+wPrDRmGfchLDUmf6CffaUYCbu4FiId+9+dcTCDvxbABRy1C3OJ8QY7cxfJ+pEZW18fRJ0XCl/fiV/ecAOfB3HsqgTzAn555h0rkFgay0hAvMU/mAW/CFNSIxV397zm749ZNLA0L2dMy1AKuOqH+/B+/ImBfJMDjmdyJQ8WU/OFRuGLdqOd2oZrA1iuPIa+yUYyZkaZfz/emQwpIL1+Q4p1R/OplA4yc301AqruXXUcVDbEB+joHW3hy5FwK5t5OwTKatrSJBkydSF9zdXy98fYzGniRyRA65P0Ix/8J3BYB4edY2/w0Ip/mdYsYQljBY0A== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2023-12-04 at 15:39 -0800, Andrii Nakryiko wrote: [...] > @@ -6845,7 +6845,47 @@ int btf_prepare_func_args(struct bpf_verifier_env = *env, int subprog) > * Only PTR_TO_CTX and SCALAR are supported atm. > */ > for (i =3D 0; i < nargs; i++) { > + bool is_nonnull =3D false; > + const char *tag; > + > t =3D btf_type_by_id(btf, args[i].type); > + > + tag =3D btf_find_decl_tag_value(btf, fn_t, i, "arg:"); Nit: this does a linear scan over all BTF type ids for each function parameter, which is kind of ugly. > + if (IS_ERR(tag) && PTR_ERR(tag) =3D=3D -ENOENT) { > + tag =3D NULL; > + } else if (IS_ERR(tag)) { > + bpf_log(log, "arg#%d type's tag fetching failure: %ld\n", i, PTR_ERR(= tag)); > + return PTR_ERR(tag); > + } > + /* 'arg:' decl_tag takes precedence over derivation of > + * register type from BTF type itself > + */ > + if (tag) { > + /* disallow arg tags in static subprogs */ > + if (!is_global) { > + bpf_log(log, "arg#%d type tag is not supported in static functions\n= ", i); > + return -EOPNOTSUPP; > + } Nit: this would be annoying if someone would add/remove 'static' a few times while developing BPF program. Are there safety reasons to forbid this? [...] > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 5787b7fd16ba..61e778dbde10 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -9268,9 +9268,30 @@ static int btf_check_func_arg_match(struct bpf_ver= ifier_env *env, int subprog, > ret =3D check_func_arg_reg_off(env, reg, regno, ARG_DONTCARE); > if (ret < 0) > return ret; > - > if (check_mem_reg(env, reg, regno, arg->mem_size)) > return -EINVAL; > + if (!(arg->arg_type & PTR_MAYBE_NULL) && (reg->type & PTR_MAYBE_NULL)= ) { > + bpf_log(log, "arg#%d is expected to be non-NULL\n", i); > + return -EINVAL; > + } > + } else if (arg->arg_type =3D=3D ARG_PTR_TO_PACKET_META) { > + if (reg->type !=3D PTR_TO_PACKET_META) { > + bpf_log(log, "arg#%d expected pkt_meta, but got %s\n", > + i, reg_type_str(env, reg->type)); > + return -EINVAL; > + } > + } else if (arg->arg_type =3D=3D ARG_PTR_TO_PACKET_DATA) { > + if (reg->type !=3D PTR_TO_PACKET) { I think it is necessary to check that 'reg->umax_value =3D=3D 0'. check_packet_access() uses reg->umax_value to bump env->prog->aux->max_pkt_offset. When body of a global function is verified it starts with 'umax_value =3D=3D 0'. Might be annoying from usability POV, however. > + bpf_log(log, "arg#%d expected pkt, but got %s\n", > + i, reg_type_str(env, reg->type)); > + return -EINVAL; > + } > + } else if (arg->arg_type =3D=3D ARG_PTR_TO_PACKET_END) { > + if (reg->type !=3D PTR_TO_PACKET_END) { > + bpf_log(log, "arg#%d expected pkt_end, but got %s\n", > + i, reg_type_str(env, reg->type)); > + return -EINVAL; > + } > } else { > bpf_log(log, "verifier bug: unrecognized arg#%d type %d\n", > i, arg->arg_type); [...]