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Thu, 06 Mar 2025 01:24:18 -0800 (PST) Received: from krava ([173.38.220.57]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac2394825efsm62758066b.45.2025.03.06.01.24.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Mar 2025 01:24:17 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 6 Mar 2025 10:24:15 +0100 To: Mykyta Yatsenko Cc: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com, eddyz87@gmail.com, Mykyta Yatsenko Subject: Re: [PATCH bpf-next v2 1/4] bpf: BPF token support for BPF_BTF_GET_FD_BY_ID Message-ID: References: <20250305194942.123191-1-mykyta.yatsenko5@gmail.com> <20250305194942.123191-2-mykyta.yatsenko5@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250305194942.123191-2-mykyta.yatsenko5@gmail.com> On Wed, Mar 05, 2025 at 07:49:39PM +0000, Mykyta Yatsenko wrote: > From: Mykyta Yatsenko > > Currently BPF_BTF_GET_FD_BY_ID requires CAP_SYS_ADMIN, which does not > allow running it from user namespace. This creates a problem when > freplace program running from user namespace needs to query target > program BTF. > This patch relaxes capable check from CAP_SYS_ADMIN to CAP_BPF and adds > support for BPF token that can be passed in attributes to syscall. > > Signed-off-by: Mykyta Yatsenko > --- > include/uapi/linux/bpf.h | 1 + > kernel/bpf/syscall.c | 9 +++++++-- > tools/include/uapi/linux/bpf.h | 1 + > .../selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c | 3 +-- > 4 files changed, 10 insertions(+), 4 deletions(-) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index bb37897c0393..73c23daacabf 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -1652,6 +1652,7 @@ union bpf_attr { > }; > __u32 next_id; > __u32 open_flags; > + __s32 token_fd; > }; > > struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */ > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 57a438706215..6975d391bb05 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -5137,14 +5137,19 @@ static int bpf_btf_load(const union bpf_attr *attr, bpfptr_t uattr, __u32 uattr_ > return btf_new_fd(attr, uattr, uattr_size); > } > > -#define BPF_BTF_GET_FD_BY_ID_LAST_FIELD btf_id > +#define BPF_BTF_GET_FD_BY_ID_LAST_FIELD token_fd > > static int bpf_btf_get_fd_by_id(const union bpf_attr *attr) > { > + struct bpf_token *token = NULL; > + > if (CHECK_ATTR(BPF_BTF_GET_FD_BY_ID)) > return -EINVAL; > > - if (!capable(CAP_SYS_ADMIN)) > + if (attr->open_flags & BPF_F_TOKEN_FD) > + token = bpf_token_get_from_fd(attr->token_fd); hi, I think you need to check token in here with IS_ERR(token) and call bpf_token_allow_cmd > + > + if (!bpf_token_capable(token, CAP_SYS_ADMIN)) and bpf_token_put in here jirka > return -EPERM; > > return btf_get_fd_by_id(attr->btf_id); > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h > index bb37897c0393..73c23daacabf 100644 > --- a/tools/include/uapi/linux/bpf.h > +++ b/tools/include/uapi/linux/bpf.h > @@ -1652,6 +1652,7 @@ union bpf_attr { > }; > __u32 next_id; > __u32 open_flags; > + __s32 token_fd; > }; > > struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */ > diff --git a/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c b/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c > index a3f238f51d05..976ff38a6d43 100644 > --- a/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c > +++ b/tools/testing/selftests/bpf/prog_tests/libbpf_get_fd_by_id_opts.c > @@ -75,9 +75,8 @@ void test_libbpf_get_fd_by_id_opts(void) > if (!ASSERT_EQ(ret, -EINVAL, "bpf_link_get_fd_by_id_opts")) > goto close_prog; > > - /* BTF get fd with opts set should not work (no kernel support). */ > ret = bpf_btf_get_fd_by_id_opts(0, &fd_opts_rdonly); > - ASSERT_EQ(ret, -EINVAL, "bpf_btf_get_fd_by_id_opts"); > + ASSERT_EQ(ret, -ENOENT, "bpf_btf_get_fd_by_id_opts"); > > close_prog: > if (fd >= 0) > -- > 2.48.1 > >