From nobody Mon Sep 16 19:36:09 2024 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 3787E1448EF; Thu, 25 Jul 2024 23:47:25 +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=1721951246; cv=none; b=FsO7pUNJQF4vwX3hHkEvxe9KgsOgjNqk3qERMUbM3gFmLord3K6QC4myvZM1yitW19aXOFRCHymrOZSDYjkoI1bMYEHSU1mXmV13U/q4jQ202KUUQehNh6a0JaXMyte+ZaCII1Klc+yr60PusP5tvO7SIv5bV4vPPc4Ua7ZByWs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721951246; c=relaxed/simple; bh=0UKtj6o3RWTCtZZLR5vBaT2vQGLsXGl2qOxqirhhQiw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=XfCTuZPiy4rQx3ln+tbCNufpcgSMz3Uqz7P3EsHQBaPBtI0jy5zlZSdIQ5cO/8cw6cZB5/39IF9kZQ2kvSn5ozs0bHZ3aHYsgHeRgle26BVwVtm/Fmb0mk/zeOoRQN1HehTgCSFIS7nwLckkm2IAeCeMGRjJO3fiUd9/I5kgKiQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JxckO7u+; 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="JxckO7u+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 812A0C116B1; Thu, 25 Jul 2024 23:47:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1721951245; bh=0UKtj6o3RWTCtZZLR5vBaT2vQGLsXGl2qOxqirhhQiw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JxckO7u+VhnbKiZ5TRGo7/l/3q0LnWJxFnUx+UcuOuNLVQgRWwgq8HRnCye+Fvc71 1rEY0xENW7E7XBj92Qix13qJD+1Gfxnzi7s/xkjaGeLoAHcsUmcIOsnzRFqKLToXfH 9cYT0/c0b91blB3wRRIrEiQWbg1ps4XHaMyz+nLaucH47P2Fu9F81WN9ufaWAWK6iV IooSLNHcieZ+/e4JV061cC89RcgZmOm7YlMcroYJrDCcU7jqVL8Bxn0WyUSN/WOkOm nsD6jqCXMBlbVlhiGUep4fmNA8fUVaBuN9OkJxAevTbkEmekytJ+H9A9ijkeDfywTG rR0Gzg+xhOaxw== 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, Song Liu Subject: [PATCH bpf-next 1/2] bpf: Add kfunc bpf_get_dentry_xattr() to read xattr from dentry Date: Thu, 25 Jul 2024 16:47:05 -0700 Message-ID: <20240725234706.655613-2-song@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240725234706.655613-1-song@kernel.org> References: <20240725234706.655613-1-song@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The primary use case here is to read xattr for directories from BPF programs. This feature enables tagging all the files in a directory with a xattr on the directory. More specifically, starting from LSM hook security_file_open(), we can read xattr of the file's parent directories. To have referenced access to dentry, a few more kfuncs are added: - bpf_file_dentry - bpf_dget_parent - bpf_dput Both bpf_file_dentry and bpf_dget_parent take a reference to the dentry (KF_ACQUIRE), which has to be released by bpf_dput (KF_RELEASE). This makes sure only trusted pointers (KF_TRUSTED_ARGS) can be used for the dentry. Note that, file_dentry() doesn't take reference to the dentry, but bpf_file_dentry() does. Signed-off-by: Song Liu --- kernel/trace/bpf_trace.c | 60 ++++++++++++++++++++++++++++++++++------ 1 file changed, 51 insertions(+), 9 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index cd098846e251..b8e6eeabb773 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1443,22 +1443,21 @@ late_initcall(bpf_key_sig_kfuncs_init); __bpf_kfunc_start_defs(); =20 /** - * bpf_get_file_xattr - get xattr of a file - * @file: file to get xattr from + * bpf_get_dentry_xattr - get xattr of a dentry + * @dentry: dentry to get xattr from * @name__str: name of the xattr * @value_p: output buffer of the xattr value * - * Get xattr *name__str* of *file* and store the output in *value_ptr*. + * Get xattr *name__str* of *dentry* and store the output in *value_ptr*. * * For security reasons, only *name__str* with prefix "user." is allowed. * * Return: 0 on success, a negative value on error. */ -__bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__st= r, - struct bpf_dynptr *value_p) +__bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *na= me__str, + struct bpf_dynptr *value_p) { struct bpf_dynptr_kern *value_ptr =3D (struct bpf_dynptr_kern *)value_p; - struct dentry *dentry; u32 value_len; void *value; int ret; @@ -1471,20 +1470,63 @@ __bpf_kfunc int bpf_get_file_xattr(struct file *fil= e, const char *name__str, if (!value) return -EINVAL; =20 - dentry =3D file_dentry(file); ret =3D inode_permission(&nop_mnt_idmap, dentry->d_inode, MAY_READ); if (ret) return ret; return __vfs_getxattr(dentry, dentry->d_inode, name__str, value, value_le= n); } =20 +/** + * bpf_get_file_xattr - get xattr of a file + * @file: file to get xattr from + * @name__str: name of the xattr + * @value_p: output buffer of the xattr value + * + * Get xattr *name__str* of *file* and store the output in *value_ptr*. + * + * For security reasons, only *name__str* with prefix "user." is allowed. + * + * Return: 0 on success, a negative value on error. + */ +__bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__st= r, + struct bpf_dynptr *value_p) +{ + struct dentry *dentry; + + dentry =3D file_dentry(file); + return bpf_get_dentry_xattr(dentry, name__str, value_p); +} + +__bpf_kfunc struct dentry *bpf_file_dentry(const struct file *file) +{ + /* file_dentry() does not hold reference to the dentry. We add a + * dget() here so that we can add KF_ACQUIRE flag to + * bpf_file_dentry(). + */ + return dget(file_dentry(file)); +} + +__bpf_kfunc struct dentry *bpf_dget_parent(struct dentry *dentry) +{ + return dget_parent(dentry); +} + +__bpf_kfunc void bpf_dput(struct dentry *dentry) +{ + return dput(dentry); +} + __bpf_kfunc_end_defs(); =20 BTF_KFUNCS_START(fs_kfunc_set_ids) +BTF_ID_FLAGS(func, bpf_get_dentry_xattr, KF_SLEEPABLE | KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_get_file_xattr, KF_SLEEPABLE | KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_file_dentry, KF_TRUSTED_ARGS | KF_ACQUIRE) +BTF_ID_FLAGS(func, bpf_dget_parent, KF_TRUSTED_ARGS | KF_ACQUIRE) +BTF_ID_FLAGS(func, bpf_dput, KF_RELEASE) BTF_KFUNCS_END(fs_kfunc_set_ids) =20 -static int bpf_get_file_xattr_filter(const struct bpf_prog *prog, u32 kfun= c_id) +static int fs_kfunc_filter(const struct bpf_prog *prog, u32 kfunc_id) { if (!btf_id_set8_contains(&fs_kfunc_set_ids, kfunc_id)) return 0; @@ -1496,7 +1538,7 @@ static int bpf_get_file_xattr_filter(const struct bpf= _prog *prog, u32 kfunc_id) static const struct btf_kfunc_id_set bpf_fs_kfunc_set =3D { .owner =3D THIS_MODULE, .set =3D &fs_kfunc_set_ids, - .filter =3D bpf_get_file_xattr_filter, + .filter =3D fs_kfunc_filter, }; =20 static int __init bpf_fs_kfuncs_init(void) --=20 2.43.0 From nobody Mon Sep 16 19:36:09 2024 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 47A6E1448EF; Thu, 25 Jul 2024 23:47:33 +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=1721951253; cv=none; b=PFvTwNU+v22C4ZQd6GaYxZ+zdZSa/tJwfCSiusU5YlHllUmr7x6JyW/HyOISKcKb+GZkKgoiR4OZSeWqNwNM2PZKwK22DIKdrBEaflyZmVDSvwTxerydvRo1x0KhUWCnC0LUDEwIcnLWuFrvut8G5IS8FuIpmiGC3aCHeqWcPe8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721951253; c=relaxed/simple; bh=PUgjQxlKWaIMqyGx3fXaZXi8AHfHJ5blsyfSLofmLmI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hBIAVrlXkNHXifm/HF2FHNqOHDghDdUX5wkPyDFzBPaErxWbAKtE6wSJ4RsQbTDO2GRIWHFyjFqWxz5Z1jD2iNCkBqkNZl//AsLEtJrqOAQtsa0GoI1waMNrJNYI7q0CV1T5prImWTWCjdnGqK1PGGSqRQYBKdSTmzqoLbz/yxY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mqXj1E3D; 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="mqXj1E3D" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D644CC116B1; Thu, 25 Jul 2024 23:47:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1721951253; bh=PUgjQxlKWaIMqyGx3fXaZXi8AHfHJ5blsyfSLofmLmI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mqXj1E3D1YE5rgAvYstkrGs85MXZah8kIjgzJRDRuQS5jDD/i4oV4b7Swsotj9jxR CX/3I7rIpjUWIubBmAw4Oe+kGZjA3eHyr19dd6IYtkVF61LBDsmldFtqWzuEqmD+fT nMjvgeOh1UiHpX3hvQfint350c+53R4L8TbD+V5zSnudbQwicwKommxhPYkPu2iyMc 7Vr9aGlx03SRjS2EXP/M4zcCKrJtIviJZVgfX/+Htwe9d6KbSKRJ8bYLg+MxAwrona dbbx/t/STEShG3UkYy3ZNBc/pW0vGcDdP1WNt+hW9NzD+INDPhiCvxIUyAoS1vMkHv C2HHtPxQq+EyA== 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, Song Liu Subject: [PATCH bpf-next 2/2] selftests/bpf: Add tests for bpf_get_dentry_xattr Date: Thu, 25 Jul 2024 16:47:06 -0700 Message-ID: <20240725234706.655613-3-song@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240725234706.655613-1-song@kernel.org> References: <20240725234706.655613-1-song@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 1. Rename fs_kfuncs/xattr to fs_kfuncs/file_xattr and add a call of bpf_get_dentry_xattr() to the test. 2. Add a new sub test fs_kfuncs/dentry_xattr, which checks 3 levels of parent directories for xattr. This demonstrate the use case that a xattr on a directory is used to tag all files in the directory and sub directories. Signed-off-by: Song Liu --- .../selftests/bpf/prog_tests/fs_kfuncs.c | 61 +++++++++++++++++-- .../selftests/bpf/progs/test_dentry_xattr.c | 46 ++++++++++++++ .../selftests/bpf/progs/test_get_xattr.c | 16 ++++- 3 files changed, 117 insertions(+), 6 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/test_dentry_xattr.c diff --git a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c b/tools/tes= ting/selftests/bpf/prog_tests/fs_kfuncs.c index 37056ba73847..a960cfbe8907 100644 --- a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c +++ b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c @@ -2,17 +2,19 @@ /* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */ =20 #include +#include #include #include #include #include #include #include "test_get_xattr.skel.h" +#include "test_dentry_xattr.skel.h" #include "test_fsverity.skel.h" =20 static const char testfile[] =3D "/tmp/test_progs_fs_kfuncs"; =20 -static void test_xattr(void) +static void test_file_xattr(void) { struct test_get_xattr *skel =3D NULL; int fd =3D -1, err; @@ -50,7 +52,8 @@ static void test_xattr(void) if (!ASSERT_GE(fd, 0, "open_file")) goto out; =20 - ASSERT_EQ(skel->bss->found_xattr, 1, "found_xattr"); + ASSERT_EQ(skel->bss->found_xattr_from_file, 1, "found_xattr_from_file"); + ASSERT_EQ(skel->bss->found_xattr_from_dentry, 1, "found_xattr_from_dentry= "); =20 out: close(fd); @@ -58,6 +61,53 @@ static void test_xattr(void) remove(testfile); } =20 +static void test_directory_xattr(void) +{ + struct test_dentry_xattr *skel =3D NULL; + static const char * const paths[] =3D { + "/tmp/a", + "/tmp/a/b", + "/tmp/a/b/c", + }; + const char *file =3D "/tmp/a/b/c/d"; + int i, j, err, fd; + + for (i =3D 0; i < sizeof(paths) / sizeof(char *); i++) { + err =3D mkdir(paths[i], 0755); + if (!ASSERT_OK(err, "mkdir")) + goto out; + err =3D setxattr(paths[i], "user.kfunc", "hello", sizeof("hello"), 0); + if (!ASSERT_OK(err, "setxattr")) { + i++; + goto out; + } + } + + skel =3D test_dentry_xattr__open_and_load(); + + if (!ASSERT_OK_PTR(skel, "test_dentry_xattr__open_and_load")) + goto out; + + skel->bss->monitored_pid =3D getpid(); + err =3D test_dentry_xattr__attach(skel); + + if (!ASSERT_OK(err, "test_dentry__xattr__attach")) + goto out; + + fd =3D open(file, O_CREAT | O_RDONLY, 0644); + if (!ASSERT_GE(fd, 0, "open_file")) + goto out; + + ASSERT_EQ(skel->bss->number_of_xattr_found, 3, "number_of_xattr_found"); + close(fd); +out: + test_dentry_xattr__destroy(skel); + remove(file); + for (j =3D i - 1; j >=3D 0; j--) + rmdir(paths[j]); +} + + #ifndef SHA256_DIGEST_SIZE #define SHA256_DIGEST_SIZE 32 #endif @@ -134,8 +184,11 @@ static void test_fsverity(void) =20 void test_fs_kfuncs(void) { - if (test__start_subtest("xattr")) - test_xattr(); + if (test__start_subtest("file_xattr")) + test_file_xattr(); + + if (test__start_subtest("dentry_xattr")) + test_directory_xattr(); =20 if (test__start_subtest("fsverity")) test_fsverity(); diff --git a/tools/testing/selftests/bpf/progs/test_dentry_xattr.c b/tools/= testing/selftests/bpf/progs/test_dentry_xattr.c new file mode 100644 index 000000000000..d2e378b2e2d5 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_dentry_xattr.c @@ -0,0 +1,46 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */ + +#include "vmlinux.h" +#include +#include "bpf_kfuncs.h" + +char _license[] SEC("license") =3D "GPL"; + +__u32 monitored_pid; +__u32 number_of_xattr_found; + +static const char expected_value[] =3D "hello"; +char value[32]; + +SEC("lsm.s/file_open") +int BPF_PROG(test_file_open, struct file *f) +{ + struct bpf_dynptr value_ptr; + struct dentry *dentry, *prev_dentry; + __u32 pid, matches =3D 0; + int i, ret; + + pid =3D bpf_get_current_pid_tgid() >> 32; + if (pid !=3D monitored_pid) + return 0; + + bpf_dynptr_from_mem(value, sizeof(value), 0, &value_ptr); + + dentry =3D bpf_file_dentry(f); + + for (i =3D 0; i < 10; i++) { + ret =3D bpf_get_dentry_xattr(dentry, "user.kfunc", &value_ptr); + if (ret =3D=3D sizeof(expected_value) && + !bpf_strncmp(value, ret, expected_value)) + matches++; + + prev_dentry =3D dentry; + dentry =3D bpf_dget_parent(prev_dentry); + bpf_dput(prev_dentry); + } + + bpf_dput(dentry); + number_of_xattr_found =3D matches; + return 0; +} diff --git a/tools/testing/selftests/bpf/progs/test_get_xattr.c b/tools/tes= ting/selftests/bpf/progs/test_get_xattr.c index 7eb2a4e5a3e5..3b0dc6106ca5 100644 --- a/tools/testing/selftests/bpf/progs/test_get_xattr.c +++ b/tools/testing/selftests/bpf/progs/test_get_xattr.c @@ -9,7 +9,8 @@ char _license[] SEC("license") =3D "GPL"; =20 __u32 monitored_pid; -__u32 found_xattr; +__u32 found_xattr_from_file; +__u32 found_xattr_from_dentry; =20 static const char expected_value[] =3D "hello"; char value[32]; @@ -18,6 +19,7 @@ SEC("lsm.s/file_open") int BPF_PROG(test_file_open, struct file *f) { struct bpf_dynptr value_ptr; + struct dentry *dentry; __u32 pid; int ret; =20 @@ -32,6 +34,16 @@ int BPF_PROG(test_file_open, struct file *f) return 0; if (bpf_strncmp(value, ret, expected_value)) return 0; - found_xattr =3D 1; + found_xattr_from_file =3D 1; + + dentry =3D bpf_file_dentry(f); + ret =3D bpf_get_dentry_xattr(dentry, "user.kfuncs", &value_ptr); + bpf_dput(dentry); + if (ret !=3D sizeof(expected_value)) + return 0; + if (bpf_strncmp(value, ret, expected_value)) + return 0; + found_xattr_from_dentry =3D 1; + return 0; } --=20 2.43.0