From patchwork Tue Jul 30 23:08:04 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13747962 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 E870318DF62; Tue, 30 Jul 2024 23:08:42 +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=1722380923; cv=none; b=sgu6XLpAlOExXIr8DI9+64jpm0i0Em6flk099gE708eu2dvcJgmSID8fXP76q3ORWyVyq7s95VH7cBUt0js8FRCwN1xtKJz6h4BkESBbRGxwAQtRlV9Iiq4fee6Jqu0STknrffu5+STykizRuDn+8Sr6iyp7bVmd5V0NRI3P+tU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722380923; c=relaxed/simple; bh=0mco/AwJ18clzdrzQJjd8uBMHcSAGTc3tSetHaJYDWs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GRuh6qAxDipKPkYt28gP5W6Vtc2UwpCjzPp2GN8DO4OcxzZaT1yaZ723ubsC57sklPJ4gGqEL/7Lab7GamTdVJWMUuNBKWGmf5ZgofP+uf7wDTNkKZjQDEGDa1NiHxWwpYpUzrUfa16NeXdQmAwA4DmjD6/rLea/2lTmJP10jXY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kOpaoZG6; 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="kOpaoZG6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A87C5C32782; Tue, 30 Jul 2024 23:08:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722380922; bh=0mco/AwJ18clzdrzQJjd8uBMHcSAGTc3tSetHaJYDWs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kOpaoZG6ktUUZRgJEL9fPuauF/E7H+Ac1Sc7gYN6/Vc6W5DAFHpbvHIDmVvx9DPFL 0gM541sMw3GfdWXjIM5yYvuUNjZwWtUt0zmVP4n+GZ/YC63LttLLN0qMTOKcfc8KSS mJaP7adF5s7vXqo7Fm4y3olsdoSMFKdrYA3U+rAuVJ1+ZAvFuG+wTalaedEbdr+JKQ QUfo/grz3mz2V6JmN72fbu92PObfh5sWsh8b80L0pOXKh9v4ez2B/uWnNUF+Q+uQFY xqqxk/YU7nA/yQ6EVxe3xu35OTIVIWDLrU5zUloR68RgNLSG6eTI3gUTqXl6H5ks0E t6LjBq1GgCkPg== 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, liamwisehart@meta.com, lltang@meta.com, shankaran@meta.com, Song Liu Subject: [PATCH v2 bpf-next 1/2] bpf: Add kfunc bpf_get_dentry_xattr() to read xattr from dentry Date: Tue, 30 Jul 2024 16:08:04 -0700 Message-ID: <20240730230805.42205-2-song@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240730230805.42205-1-song@kernel.org> References: <20240730230805.42205-1-song@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This kfunc can be used in LSM hooks with dentry, such as: security_inode_listxattr security_inode_permission and many more. Signed-off-by: Song Liu --- kernel/trace/bpf_trace.c | 46 ++++++++++++++++++++++++++++++---------- 1 file changed, 35 insertions(+), 11 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index cd098846e251..c62a00975f92 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1443,26 +1443,29 @@ late_initcall(bpf_key_sig_kfuncs_init); __bpf_kfunc_start_defs(); /** - * 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__str, - struct bpf_dynptr *value_p) +__bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__str, + struct bpf_dynptr *value_p) { struct bpf_dynptr_kern *value_ptr = (struct bpf_dynptr_kern *)value_p; - struct dentry *dentry; + struct inode *inode = d_inode(dentry); u32 value_len; void *value; int ret; + if (WARN_ON(!inode)) + return -EINVAL; + if (strncmp(name__str, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) return -EPERM; @@ -1471,20 +1474,41 @@ __bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__str, if (!value) return -EINVAL; - dentry = file_dentry(file); - ret = inode_permission(&nop_mnt_idmap, dentry->d_inode, MAY_READ); + ret = inode_permission(&nop_mnt_idmap, inode, MAY_READ); if (ret) return ret; - return __vfs_getxattr(dentry, dentry->d_inode, name__str, value, value_len); + return __vfs_getxattr(dentry, inode, name__str, value, value_len); +} + +/** + * 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__str, + struct bpf_dynptr *value_p) +{ + struct dentry *dentry; + + dentry = file_dentry(file); + return bpf_get_dentry_xattr(dentry, name__str, value_p); } __bpf_kfunc_end_defs(); 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_KFUNCS_END(fs_kfunc_set_ids) -static int bpf_get_file_xattr_filter(const struct bpf_prog *prog, u32 kfunc_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 +1520,7 @@ 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 = { .owner = THIS_MODULE, .set = &fs_kfunc_set_ids, - .filter = bpf_get_file_xattr_filter, + .filter = fs_kfunc_filter, }; static int __init bpf_fs_kfuncs_init(void) From patchwork Tue Jul 30 23:08:05 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Song Liu X-Patchwork-Id: 13747963 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 40B18192B79; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="r82Fqb1d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13AC5C32782; Tue, 30 Jul 2024 23:08:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722380930; bh=lq0Jt38kp2fXgQbfobxahLQ7bZKvnshoeyfcUDDAytw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=r82Fqb1ddLUenHwSTFfaISuxTJo0dmiGXTrddyW/4S73dsY3w4fatlJYspwfcWDQk PTIcW1Qad851Hsxtrwn9He0faQjmJC8w5uAKB8ykXKJbyXl+T1HQyun7g8icW6nVNM YAmrmhASjY9JvmPS+2YYefBVtRDdvOJ0hOaPORvXAVetFe+ubFb6nctnfTrslMr/WT Sy1Jm27lP9U+B1mMXR3pt2midurVF8ICje/K/MDx46K4wF7bPPIXY2S2dd8c3d+xcc 4wU1jpGlNeGUGMspEkhIra2X7HHpIcj2R8pmAbjhwUwFD5QFjMpofTtMWN7ho1G1nk 0R0qQEoy9JD6Q== 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, liamwisehart@meta.com, lltang@meta.com, shankaran@meta.com, Song Liu Subject: [PATCH v2 bpf-next 2/2] selftests/bpf: Add tests for bpf_get_dentry_xattr Date: Tue, 30 Jul 2024 16:08:05 -0700 Message-ID: <20240730230805.42205-3-song@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240730230805.42205-1-song@kernel.org> References: <20240730230805.42205-1-song@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Add test for bpf_get_dentry_xattr on hook security_inode_getxattr. Verify that the kfunc can read the xattr. Also test failing getxattr from user space by returning non-zero from the LSM bpf program. Signed-off-by: Song Liu --- .../selftests/bpf/prog_tests/fs_kfuncs.c | 9 ++++- .../selftests/bpf/progs/test_get_xattr.c | 37 ++++++++++++++++--- 2 files changed, 40 insertions(+), 6 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c index 37056ba73847..5a0b51157451 100644 --- a/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c +++ b/tools/testing/selftests/bpf/prog_tests/fs_kfuncs.c @@ -16,6 +16,7 @@ static void test_xattr(void) { struct test_get_xattr *skel = NULL; int fd = -1, err; + int v[32]; fd = open(testfile, O_CREAT | O_RDONLY, 0644); if (!ASSERT_GE(fd, 0, "create_file")) @@ -50,7 +51,13 @@ static void test_xattr(void) if (!ASSERT_GE(fd, 0, "open_file")) goto out; - ASSERT_EQ(skel->bss->found_xattr, 1, "found_xattr"); + ASSERT_EQ(skel->bss->found_xattr_from_file, 1, "found_xattr_from_file"); + + /* Trigger security_inode_getxattr */ + err = getxattr(testfile, "user.kfuncs", v, sizeof(v)); + ASSERT_EQ(err, -1, "getxattr_return"); + ASSERT_EQ(errno, EINVAL, "getxattr_errno"); + ASSERT_EQ(skel->bss->found_xattr_from_dentry, 1, "found_xattr_from_dentry"); out: close(fd); diff --git a/tools/testing/selftests/bpf/progs/test_get_xattr.c b/tools/testing/selftests/bpf/progs/test_get_xattr.c index 7eb2a4e5a3e5..66e737720f7c 100644 --- a/tools/testing/selftests/bpf/progs/test_get_xattr.c +++ b/tools/testing/selftests/bpf/progs/test_get_xattr.c @@ -2,6 +2,7 @@ /* Copyright (c) 2023 Meta Platforms, Inc. and affiliates. */ #include "vmlinux.h" +#include #include #include #include "bpf_kfuncs.h" @@ -9,10 +10,12 @@ char _license[] SEC("license") = "GPL"; __u32 monitored_pid; -__u32 found_xattr; +__u32 found_xattr_from_file; +__u32 found_xattr_from_dentry; static const char expected_value[] = "hello"; -char value[32]; +char value1[32]; +char value2[32]; SEC("lsm.s/file_open") int BPF_PROG(test_file_open, struct file *f) @@ -25,13 +28,37 @@ int BPF_PROG(test_file_open, struct file *f) if (pid != monitored_pid) return 0; - bpf_dynptr_from_mem(value, sizeof(value), 0, &value_ptr); + bpf_dynptr_from_mem(value1, sizeof(value1), 0, &value_ptr); ret = bpf_get_file_xattr(f, "user.kfuncs", &value_ptr); if (ret != sizeof(expected_value)) return 0; - if (bpf_strncmp(value, ret, expected_value)) + if (bpf_strncmp(value1, ret, expected_value)) return 0; - found_xattr = 1; + found_xattr_from_file = 1; return 0; } + +SEC("lsm.s/inode_getxattr") +int BPF_PROG(test_inode_getxattr, struct dentry *dentry, char *name) +{ + struct bpf_dynptr value_ptr; + __u32 pid; + int ret; + + pid = bpf_get_current_pid_tgid() >> 32; + if (pid != monitored_pid) + return 0; + + bpf_dynptr_from_mem(value2, sizeof(value2), 0, &value_ptr); + + ret = bpf_get_dentry_xattr(dentry, "user.kfuncs", &value_ptr); + if (ret != sizeof(expected_value)) + return 0; + if (bpf_strncmp(value2, ret, expected_value)) + return 0; + found_xattr_from_dentry = 1; + + /* return non-zero to fail getxattr from user space */ + return -EINVAL; +}