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Mon, 17 Mar 2025 10:40:46 -0700 (PDT) Received: from msi-laptop.thefacebook.com ([2620:10d:c092:500::4:812]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac3147e9cadsm693917166b.48.2025.03.17.10.40.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Mar 2025 10:40:45 -0700 (PDT) From: Mykyta Yatsenko To: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com, eddyz87@gmail.com, olsajiri@gmail.com, yonghong.song@linux.dev Cc: Mykyta Yatsenko Subject: [PATCH bpf-next v6 1/4] bpf: BPF token support for BPF_BTF_GET_FD_BY_ID Date: Mon, 17 Mar 2025 17:40:36 +0000 Message-ID: <20250317174039.161275-2-mykyta.yatsenko5@gmail.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250317174039.161275-1-mykyta.yatsenko5@gmail.com> References: <20250317174039.161275-1-mykyta.yatsenko5@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net 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 | 23 +++++++++++++++++++++-- tools/include/uapi/linux/bpf.h | 1 + 3 files changed, 23 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index bb37897c0393..661de2444965 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 fd_by_id_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 6a8f20ee2851..419f82c78203 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -5120,15 +5120,34 @@ 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 fd_by_id_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) + return -EINVAL; + + if (attr->open_flags & BPF_F_TOKEN_FD) { + token = bpf_token_get_from_fd(attr->fd_by_id_token_fd); + if (IS_ERR(token)) + return PTR_ERR(token); + if (!bpf_token_allow_cmd(token, BPF_BTF_GET_FD_BY_ID)) { + bpf_token_put(token); + token = NULL; + } + } + + if (!bpf_token_capable(token, CAP_SYS_ADMIN)) { + bpf_token_put(token); return -EPERM; + } + + bpf_token_put(token); 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..661de2444965 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 fd_by_id_token_fd; }; struct { /* anonymous struct used by BPF_OBJ_GET_INFO_BY_FD */