From patchwork Wed Dec 18 00:56:28 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wenbo Zhang X-Patchwork-Id: 1211861 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="omEythYb"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 47cxRJ3sbxz9sRl for ; Wed, 18 Dec 2019 11:56:44 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726664AbfLRA4n (ORCPT ); Tue, 17 Dec 2019 19:56:43 -0500 Received: from mail-pj1-f68.google.com ([209.85.216.68]:37638 "EHLO mail-pj1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726333AbfLRA4n (ORCPT ); Tue, 17 Dec 2019 19:56:43 -0500 Received: by mail-pj1-f68.google.com with SMTP id m13so53219pjb.2; Tue, 17 Dec 2019 16:56:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :in-reply-to:references; bh=pskpn4pZcU1qHjwxK0Qy4bRCuU/IP4PVYEYVbKI+XOM=; b=omEythYbo1xdcCei1TE9glZBI9+gVmKcGiZJ60sKnhsAIcC3iPXY8iqmaqyOx08Lj6 dWRkiDTujdtT165MHa3pa5f/IhBjK+Q4xZ9cPoFeVir/8VqDY0BvgY3VzZbFp4TrJLv0 eQCD63zurTi8KISYxeg9DTeI1ifM7E4LfIaTV3WcY1ENs3WQPDeEsO2MCbB3yCccIJhJ eEORbs9RUmCYbGeCxWgNNbsuGs/M9QhB26nA8+/T7yA3RmN58o2nnSaXr623UBAjNRFM se3VAXzwzIKs8xIHXQ/UL0yqXQgnTU/MILOuNXblBb14druumtT11G+Rb6RsEsV+dlvu ccOQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:in-reply-to:references; bh=pskpn4pZcU1qHjwxK0Qy4bRCuU/IP4PVYEYVbKI+XOM=; b=pZQE5p+MelwmPy276Sb/pkfdbsb2VqwVZo93KMFLOxdk6otg6qfYnkFF785urJYdi0 FGj4nluniVv4Q+LTwZ2ABONsyW4HPWXhjpGELOjnOl7dMKhrN2rgPe6ceZTac8HHpd9d qfhBbjFuGivUvnp1o7hV7XmB3KpW5LZsqpMwZfsm8JniycE6b6EtH7u7ae+pqQXQMeJF 0ZVLXcYFq2o819burq+lhPZHslBnDLNaCvhkIBgrgytZVWOCFXluiKsXwG7QuNlhfNrJ P2TfQwvjjVXfLN5LRM1RsU1863zddrVYl+Hxtp2Dubf8qR3XoKt8sSYQWERSxvv2x3qg L8HQ== X-Gm-Message-State: APjAAAVCYpB6bgJN0M7dNYii3jW0OqyRoP+aYGNWAZTna8TrYF1cWCl2 tt+ypgj2W1Z2aiB1DElh7pUDDL62Y5k= X-Google-Smtp-Source: APXvYqzTli6APT3bvH/9g5R/peNDPyEcx/0IytO+2Ifx6E6nH77f3B9YUmt8C14zFrx/34ujW9OsUg== X-Received: by 2002:a17:90a:a010:: with SMTP id q16mr201907pjp.115.1576630602109; Tue, 17 Dec 2019 16:56:42 -0800 (PST) Received: from ubuntu-18.04-x8664 ([128.1.49.85]) by smtp.gmail.com with ESMTPSA id z129sm278464pfb.67.2019.12.17.16.56.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Dec 2019 16:56:41 -0800 (PST) From: Wenbo Zhang To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, yhs@fb.com, bgregg@netflix.com, andrii.nakryiko@gmail.com, netdev@vger.kernel.org Subject: [PATCH bpf-next v14 1/2] bpf: add new helper get_fd_path for mapping a file descriptor to a pathname Date: Tue, 17 Dec 2019 19:56:28 -0500 Message-Id: <7464919bd9c15f2496ca29dceb6a4048b3199774.1576629200.git.ethercflow@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: References: <8f6b8979fb64bedf5cb406ba29146c5fa2539267.1576575253.git.ethercflow@gmail.com> In-Reply-To: References: Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org When people want to identify which file system files are being opened, read, and written to, they can use this helper with file descriptor as input to achieve this goal. Other pseudo filesystems are also supported. This requirement is mainly discussed here: https://github.com/iovisor/bcc/issues/237 v13->v14: addressed Yonghong and Daniel's feedback - fix this helper's description to be consistent with comments in d_path - fix error handling logic fill zeroes not '0's v12->v13: addressed Brendan and Yonghong's feedback - rename to get_fd_path - refactor code & comment to be clearer and more compliant v11->v12: addressed Alexei's feedback - only allow tracepoints to make sure it won't dead lock v10->v11: addressed Al and Alexei's feedback - fix missing fput() v9->v10: addressed Andrii's feedback - send this patch together with the patch selftests as one patch series v8->v9: - format helper description v7->v8: addressed Alexei's feedback - use fget_raw instead of fdget_raw, as fdget_raw is only used inside fs/ - ensure we're in user context which is safe fot the help to run - filter unmountable pseudo filesystem, because they don't have real path - supplement the description of this helper function v6->v7: - fix missing signed-off-by line v5->v6: addressed Andrii's feedback - avoid unnecessary goto end by having two explicit returns v4->v5: addressed Andrii and Daniel's feedback - rename bpf_fd2path to bpf_get_file_path to be consistent with other helper's names - when fdget_raw fails, set ret to -EBADF instead of -EINVAL - remove fdput from fdget_raw's error path - use IS_ERR instead of IS_ERR_OR_NULL as d_path ether returns a pointer into the buffer or an error code if the path was too long - modify the normal path's return value to return copied string length including NUL - update this helper description's Return bits. v3->v4: addressed Daniel's feedback - fix missing fdput() - move fd2path from kernel/bpf/trace.c to kernel/trace/bpf_trace.c - move fd2path's test code to another patch - add comment to explain why use fdget_raw instead of fdget v2->v3: addressed Yonghong's feedback - remove unnecessary LOCKDOWN_BPF_READ - refactor error handling section for enhanced readability - provide a test case in tools/testing/selftests/bpf v1->v2: addressed Daniel's feedback - fix backward compatibility - add this helper description - fix signed-off name Signed-off-by: Wenbo Zhang Acked-by: Yonghong Song Tested-by: Jiri Olsa --- include/uapi/linux/bpf.h | 29 +++++++++++++- kernel/trace/bpf_trace.c | 69 ++++++++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 29 +++++++++++++- 3 files changed, 125 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index dbbcf0b02970..4534ce49f838 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2821,6 +2821,32 @@ union bpf_attr { * Return * On success, the strictly positive length of the string, including * the trailing NUL character. On error, a negative value. + * + * int bpf_get_fd_path(char *path, u32 size, int fd) + * Description + * Get **file** atrribute from the current task by *fd*, then call + * **d_path** to get it's absolute path and copy it as string into + * *path* of *size*. Notice the **path** don't support unmountable + * pseudo filesystems as they don't have path (eg: SOCKFS, PIPEFS). + * The *size* must be strictly positive. On success, the helper + * makes sure that the *path* is NUL-terminated, and the buffer + * could be: + * - a regular full path (include mountable fs eg: /proc, /sys) + * - a regular full path with " (deleted)" is appended. + * On failure, it is filled with zeroes. + * Return + * On success, returns the length of the copied string INCLUDING + * the trailing '\0'. + * + * On failure, the returned value is one of the following: + * + * **-EPERM** if no permission to get the path (eg: in irq ctx). + * + * **-EBADF** if *fd* is invalid. + * + * **-EINVAL** if *fd* corresponds to a unmountable pseudo fs + * + * **-ENAMETOOLONG** if full path is longer than *size* */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -2938,7 +2964,8 @@ union bpf_attr { FN(probe_read_user), \ FN(probe_read_kernel), \ FN(probe_read_user_str), \ - FN(probe_read_kernel_str), + FN(probe_read_kernel_str), \ + FN(get_fd_path), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index e5ef4ae9edb5..a2c18b193141 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -762,6 +762,71 @@ static const struct bpf_func_proto bpf_send_signal_proto = { .arg1_type = ARG_ANYTHING, }; +BPF_CALL_3(bpf_get_fd_path, char *, dst, u32, size, int, fd) +{ + int ret = -EBADF; + struct file *f; + char *p; + + /* Ensure we're in user context which is safe for the helper to + * run. This helper has no business in a kthread. + */ + if (unlikely(in_interrupt() || + current->flags & (PF_KTHREAD | PF_EXITING))) { + ret = -EPERM; + goto error; + } + + /* Use fget_raw instead of fget to support O_PATH, and it doesn't + * have any sleepable code, so it's ok to be here. + */ + f = fget_raw(fd); + if (!f) + goto error; + + /* For unmountable pseudo filesystem, it seems to have no meaning + * to get their fake paths as they don't have path, and to be no + * way to validate this function pointer can be always safe to call + * in the current context. + */ + if (f->f_path.dentry->d_op && f->f_path.dentry->d_op->d_dname) { + ret = -EINVAL; + fput(f); + goto error; + } + + /* After filter unmountable pseudo filesytem, d_path won't call + * dentry->d_op->d_name(), the normally path doesn't have any + * sleepable code, and despite it uses the current macro to get + * fs_struct (current->fs), we've already ensured we're in user + * context, so it's ok to be here. + */ + p = d_path(&f->f_path, dst, size); + if (IS_ERR(p)) { + ret = PTR_ERR(p); + fput(f); + goto error; + } + + ret = strlen(p) + 1; + memmove(dst, p, ret); + fput(f); + return ret; + +error: + memset(dst, 0, size); + return ret; +} + +static const struct bpf_func_proto bpf_get_fd_path_proto = { + .func = bpf_get_fd_path, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_UNINIT_MEM, + .arg2_type = ARG_CONST_SIZE, + .arg3_type = ARG_ANYTHING, +}; + static const struct bpf_func_proto * tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { @@ -953,6 +1018,8 @@ tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_stackid_proto_tp; case BPF_FUNC_get_stack: return &bpf_get_stack_proto_tp; + case BPF_FUNC_get_fd_path: + return &bpf_get_fd_path_proto; default: return tracing_func_proto(func_id, prog); } @@ -1146,6 +1213,8 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_stackid_proto_raw_tp; case BPF_FUNC_get_stack: return &bpf_get_stack_proto_raw_tp; + case BPF_FUNC_get_fd_path: + return &bpf_get_fd_path_proto; default: return tracing_func_proto(func_id, prog); } diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index dbbcf0b02970..4534ce49f838 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -2821,6 +2821,32 @@ union bpf_attr { * Return * On success, the strictly positive length of the string, including * the trailing NUL character. On error, a negative value. + * + * int bpf_get_fd_path(char *path, u32 size, int fd) + * Description + * Get **file** atrribute from the current task by *fd*, then call + * **d_path** to get it's absolute path and copy it as string into + * *path* of *size*. Notice the **path** don't support unmountable + * pseudo filesystems as they don't have path (eg: SOCKFS, PIPEFS). + * The *size* must be strictly positive. On success, the helper + * makes sure that the *path* is NUL-terminated, and the buffer + * could be: + * - a regular full path (include mountable fs eg: /proc, /sys) + * - a regular full path with " (deleted)" is appended. + * On failure, it is filled with zeroes. + * Return + * On success, returns the length of the copied string INCLUDING + * the trailing '\0'. + * + * On failure, the returned value is one of the following: + * + * **-EPERM** if no permission to get the path (eg: in irq ctx). + * + * **-EBADF** if *fd* is invalid. + * + * **-EINVAL** if *fd* corresponds to a unmountable pseudo fs + * + * **-ENAMETOOLONG** if full path is longer than *size* */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -2938,7 +2964,8 @@ union bpf_attr { FN(probe_read_user), \ FN(probe_read_kernel), \ FN(probe_read_user_str), \ - FN(probe_read_kernel_str), + FN(probe_read_kernel_str), \ + FN(get_fd_path), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call