From patchwork Fri Nov 15 10:55:27 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wenbo Zhang X-Patchwork-Id: 1195542 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="fNtnmERG"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 47DwHh1bKBz9sP4 for ; Fri, 15 Nov 2019 21:55:43 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727200AbfKOKzn (ORCPT ); Fri, 15 Nov 2019 05:55:43 -0500 Received: from mail-pg1-f194.google.com ([209.85.215.194]:36676 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726521AbfKOKzm (ORCPT ); Fri, 15 Nov 2019 05:55:42 -0500 Received: by mail-pg1-f194.google.com with SMTP id k13so5831642pgh.3; Fri, 15 Nov 2019 02:55:40 -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; bh=20Cgp80vhwwKTOz8AyAi1Y+u0+xnbO+WaqEg864mgH0=; b=fNtnmERGHmVNsnVwGDAuoXikGXWQ1cFhY90zZm8SrboL14kl1ecDEYJje/R+QoU9aB UDauDYwKORRfQBW0ANOejleEWWicWzKRfAJj/FqaPsf93OHUW8WiCKPBr8e24xgAnwwC e4aydMoEfdAh5rn70th4ov2pYzuZBovciWmM0/qQnwNDPD0gvdrmwtDJ8GkjMrYWF64z 7BZHuGzGeJ36RZmXzBri55FaeY0aiZOx6KjSGB2+DvmOMzFAob+733bBbCtXsW0W4Yrp f/hc2nGhxyVEh6kaPV1S1PKRBGb+6uZnNBbCtcjUg8ykAAKGgjLifUjopf/gAsnEfU7H lP6A== 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; bh=20Cgp80vhwwKTOz8AyAi1Y+u0+xnbO+WaqEg864mgH0=; b=MJrLbap4jK/JwScBqEMWtY1oR+kWfcJTtP/+XOzMM26ScM9KtXIG9TIcX5N/veiNF2 pZCD8a+HM4+RMv3PZOdRjyVCX08vHiksOGVuwHpbgI4ZhzE8qqx5RZkmE1AKYTSFMg90 ehCkiXJ18VF1OdYHHefy5YVo8TBhc+fiiwNU2JCG7hhZSSC9LyTePgd9bE78oj+UsFFE ITlztfC/QVHzX6wwZMs89U6Grz7NZp36LxfqzjIsraWL+XSNtMv5Ky4Z2Bhzy7BGtg6N olPn8wrEWkXq2cVaGTqmt6vwEct2TYEbBz3rmvQoGDKbluuE2JOszVyvD8NKKa21wFTW Heyg== X-Gm-Message-State: APjAAAXgVL1pzzcthKjDEEr7BgIOVIPwVUrBiuvKe/BlxqPo5CB7yAGl i6dd37WE9+3YE9vj9GQTWvULDMHFDl4= X-Google-Smtp-Source: APXvYqwxdq39mRRW2kE2hFSZsdh3QQwm7q1yRv7PqO0S8tHltxiw987Kcp6UveF7hNZpA832kFLPng== X-Received: by 2002:a65:6245:: with SMTP id q5mr8133304pgv.347.1573815339875; Fri, 15 Nov 2019 02:55:39 -0800 (PST) Received: from ubuntu-18.04-x8664 ([128.1.49.85]) by smtp.gmail.com with ESMTPSA id c9sm12515428pfb.114.2019.11.15.02.55.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Nov 2019 02:55:39 -0800 (PST) From: Wenbo Zhang To: bpf@vger.kernel.org Cc: alexei.starovoitov@gmail.com, daniel@iogearbox.net, yhs@fb.com, andrii.nakryiko@gmail.com, netdev@vger.kernel.org, Wenbo Zhang Subject: [PATCH bpf-next v8] bpf: add new helper get_file_path for mapping a file descriptor to a pathname Date: Fri, 15 Nov 2019 05:55:27 -0500 Message-Id: <20191115105527.28226-1-ethercflow@gmail.com> X-Mailer: git-send-email 2.17.1 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 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 --- include/uapi/linux/bpf.h | 29 +++++++++++++++- kernel/trace/bpf_trace.c | 63 ++++++++++++++++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 28 ++++++++++++++- 3 files changed, 118 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index df6809a76404..8ca63815fd9c 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2815,6 +2815,32 @@ 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_file_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)" at the end. + * On failure, it is filled with zeroes. + * Return + * On success, returns the length of the copied string INCLUDING + * the trailing NUL. + * + * 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), \ @@ -2932,7 +2958,8 @@ 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_file_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 ffc91d4935ac..274ecb67ea4a 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -762,6 +762,67 @@ static const struct bpf_func_proto bpf_send_signal_proto = { .arg1_type = ARG_ANYTHING, }; +BPF_CALL_3(bpf_get_file_path, char *, dst, u32, size, int, fd) +{ + struct file *f; + char *p; + int ret = -EBADF; + + /* 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))) + return -EPERM; + + /* 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) + return -EINVAL; + + /* After filter unmountable pseudo filesytem, d_path won't call + * dentry->d_op->d_name(), the noramlly 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); + memmove(dst, p, ret); + dst[ret++] = '\0'; + fput(f); + return ret; + +error: + memset(dst, '0', size); + return ret; +} + +static const struct bpf_func_proto bpf_get_file_path_proto = { + .func = bpf_get_file_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) { @@ -822,6 +883,8 @@ tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) #endif case BPF_FUNC_send_signal: return &bpf_send_signal_proto; + case BPF_FUNC_get_file_path: + return &bpf_get_file_path_proto; default: return NULL; } diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index df6809a76404..4147f628feea 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -2815,6 +2815,31 @@ 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_file_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)" at the end. + * On failure, it is filled with zeroes. + * Return + * On success, returns the length of the copied string INCLUDING + * the trailing NUL. + * + * 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), \ @@ -2932,7 +2957,8 @@ 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_file_path), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call