From patchwork Tue Oct 29 23:12:39 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13855638 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D2D420ADD4; Tue, 29 Oct 2024 23:12:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730243575; cv=none; b=AoXNcusJDOMbJ3fwjQeWVLuvEVuNh3T2QCkFuVULmY910Po/V+bXQSufZe51aXLmCNex8kKkBJyqa0ahqNNDofk978FAKHiyF5PNTISELUlhTMEiW4vF64hh+1oX//8awQ89XGgmFLl2F20DUVpETj/O5BPWtmKxHDA2fSqeUuE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730243575; c=relaxed/simple; bh=LjcugxeRFbGxnwLPmH2IHhrjSAtZ2rEER7t/y7d2bMs=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=nWqpTh98qCMVuc1zJt+X6Pn2sRz0h4pgvghcUxAKlUNPhOj9zH3aVIVU+6zJ/5ZjCW58In2erP6MiasCc8aktTXAh/3FavUM+NR6sY/d0MaAcrlciT0t4nNi1GGlzQWc933LPzIWmq8O0kgemVTRfXpHcku+XkcIZN+6bNWJDWM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=j3yo2Wf1; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="j3yo2Wf1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A5E3C4CEE3; Tue, 29 Oct 2024 23:12:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730243575; bh=LjcugxeRFbGxnwLPmH2IHhrjSAtZ2rEER7t/y7d2bMs=; h=From:To:Cc:Subject:Date:From; b=j3yo2Wf1KLjmO/WmIqJeCDal4Z6naw/DuztLhMTbuh/MsKmd71oWTXLyqDwF9Aj+E FIkkJ+tHg/j1K0buShRvT3+TaGqpgFBn0xSzMRAEQpAmsm/cJkf625KlSYTiSLp0zg tmIgBhmLs7b/3mlCXyx1JVutvKoddnbFpiY7dVd5zps6zOwmvSOcLWZUP0TFkIWg+d hzNhKpZue9cYAvBZomKbjWXIQORkxO46mvCB+HjzXl8QTEvV2dVFBOz/Q0TVwUi1nx +uEdYR4W9FiObUQX/qL++mMnxwU+HgRD8vO2T2kdvrdMXQAC9r/JZoHVUFTJKEWf+1 u0tEwnPEMqZTA== From: Song Liu To: bpf@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: kernel-team@meta.com, andrii@kernel.org, eddyz87@gmail.com, ast@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, kpsingh@kernel.org, mattbobrowski@google.com, amir73il@gmail.com, repnop@google.com, jlayton@kernel.org, josef@toxicpanda.com, Song Liu Subject: [RFC bpf-next fanotify 0/5] Fanotify fastpath handler Date: Tue, 29 Oct 2024 16:12:39 -0700 Message-ID: <20241029231244.2834368-1-song@kernel.org> X-Mailer: git-send-email 2.43.5 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This RFC set introduces in-kernel fastpath handler for fanotify. The fastpath handler can be used to handle/filter some events without going through userspace. In LPC 2024, multiple talks covered use cases of monitoring a subtree in the VFS (fanotify: [1], bpf/lsm: [2]). This work is inspired by these discussions. Reliably monitoring of a subtree with low overhead is a hard problem. We do not claim this set fully solves problem. But we think this work can be a very useful building block of the solution to this problem. The fastpath handler can be implemented with built-in logic, in a kernel module, or a bpf program. The fastpath handler is attached to a fsnotify group. With current implementation, the multiple fastpath handlers are maintained in a global list. Only users with CAP_SYS_ADMIN can add fastpath handlers to the list by loading a kernel module. User without CAP_SYS_ADMIN can attach a loaded fastpath handler to fanotify instances. During the attach operation, the fastpath handler can take an argument. This enables non-CAP_SYSADMIN users to customize/configure the fastpath handler, for example, with a specific allowlist/denylist. As the patchset grows to 1000+ lines (including samples and tests), I would like some feedback before pushing it further. Overview: Patch 1/5 adds logic to write fastpath handlers in kernel modules. Patch 2/5 adds a sample of a fastpath handler in a kernel module. Patch 3/5 is some preparation work on BPF side. Patch 4/5 adds logic to write fastpath handlers in bpf programs. Patch 5/5 is a selftest and example of bpf based fastpath handler. TODO: 1. Add some mechanism to help users discover available fastpath handlers. For example, we can add a sysctl which is similar to net.ipv4.tcp_available_congestion_control, or we can add some sysfs entries. 2. Enable prviate (not added to global list) bpf based fastpath handlers. 3. More testing for inode local storage. 4. Man pages. [1] https://lpc.events/event/18/contributions/1717/ [2] https://lpc.events/event/18/contributions/1940/ Song Liu (5): fanotify: Introduce fanotify fastpath handler samples/fanotify: Add a sample fanotify fastpath handler bpf: Make bpf inode storage available to tracing programs fanotify: Enable bpf based fanotify fastpath handler selftests/bpf: Add test for BPF based fanotify fastpath handler MAINTAINERS | 1 + fs/Makefile | 2 +- fs/bpf_fs_kfuncs.c | 23 +- fs/notify/fanotify/Makefile | 2 +- fs/notify/fanotify/fanotify.c | 25 ++ fs/notify/fanotify/fanotify_fastpath.c | 318 ++++++++++++++++++ fs/notify/fanotify/fanotify_user.c | 7 + include/linux/bpf.h | 9 + include/linux/bpf_lsm.h | 29 -- include/linux/fanotify.h | 45 +++ include/linux/fs.h | 4 + include/linux/fsnotify_backend.h | 3 + include/uapi/linux/fanotify.h | 26 ++ kernel/bpf/Makefile | 3 +- kernel/bpf/bpf_inode_storage.c | 174 +++++++--- kernel/bpf/bpf_lsm.c | 4 - kernel/bpf/verifier.c | 5 + kernel/trace/bpf_trace.c | 8 + samples/Kconfig | 20 +- samples/Makefile | 2 +- samples/fanotify/.gitignore | 1 + samples/fanotify/Makefile | 5 +- samples/fanotify/fastpath-mod.c | 138 ++++++++ samples/fanotify/fastpath-user.c | 90 +++++ security/bpf/hooks.c | 5 - tools/testing/selftests/bpf/bpf_kfuncs.h | 4 + tools/testing/selftests/bpf/config | 1 + .../testing/selftests/bpf/prog_tests/fan_fp.c | 245 ++++++++++++++ tools/testing/selftests/bpf/progs/fan_fp.c | 77 +++++ 29 files changed, 1189 insertions(+), 87 deletions(-) create mode 100644 fs/notify/fanotify/fanotify_fastpath.c create mode 100644 samples/fanotify/fastpath-mod.c create mode 100644 samples/fanotify/fastpath-user.c create mode 100644 tools/testing/selftests/bpf/prog_tests/fan_fp.c create mode 100644 tools/testing/selftests/bpf/progs/fan_fp.c --- 2.43.5