[PATCH v2 2/5] seccomp, bpf: Introduce SECCOMP_LOAD_FILTER operation

From: Hengqi Chen <hengqi.chen@gmail.com>
To: linux-kernel@vger.kernel.org, bpf@vger.kernel.org
Cc: keescook@chromium.org, ast@kernel.org, daniel@iogearbox.net,
	andrii@kernel.org, luto@amacapital.net, wad@chromium.org,
	alexyonghe@tencent.com, hengqi.chen@gmail.com
Subject: [PATCH v2 2/5] seccomp, bpf: Introduce SECCOMP_LOAD_FILTER operation
Date: Sun, 15 Oct 2023 23:29:50 +0000	[thread overview]
Message-ID: <20231015232953.84836-3-hengqi.chen@gmail.com> (raw)
In-Reply-To: <20231015232953.84836-1-hengqi.chen@gmail.com>

This patch adds a new operation named SECCOMP_LOAD_FILTER.
It accepts a sock_fprog the same as SECCOMP_SET_MODE_FILTER
but only performs the loading process. If succeed, return a
new fd associated with the JITed BPF program (the filter).
The filter can then be pinned to bpffs using the returned
fd and reused for different processes. To distinguish the
filter from other BPF progs, BPF_PROG_TYPE_SECCOMP is added.

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 include/uapi/linux/bpf.h       |  1 +
 include/uapi/linux/seccomp.h   |  1 +
 kernel/seccomp.c               | 43 ++++++++++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h |  1 +
 4 files changed, 46 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7ba61b75bc0e..61c80ffb1724 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -995,6 +995,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_LOOKUP,
 	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
 	BPF_PROG_TYPE_NETFILTER,
+	BPF_PROG_TYPE_SECCOMP,
 };
 
 enum bpf_attach_type {
diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
index dbfc9b37fcae..ee2c83697810 100644
--- a/include/uapi/linux/seccomp.h
+++ b/include/uapi/linux/seccomp.h
@@ -16,6 +16,7 @@
 #define SECCOMP_SET_MODE_FILTER		1
 #define SECCOMP_GET_ACTION_AVAIL	2
 #define SECCOMP_GET_NOTIF_SIZES		3
+#define SECCOMP_LOAD_FILTER		4
 
 /* Valid flags for SECCOMP_SET_MODE_FILTER */
 #define SECCOMP_FILTER_FLAG_TSYNC		(1UL << 0)
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index faf84fc892eb..c9f6a19f7a4e 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -17,6 +17,7 @@
 
 #include <linux/refcount.h>
 #include <linux/audit.h>
+#include <linux/bpf.h>
 #include <linux/compat.h>
 #include <linux/coredump.h>
 #include <linux/kmemleak.h>
@@ -25,6 +26,7 @@
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
 #include <linux/seccomp.h>
+#include <linux/security.h>
 #include <linux/slab.h>
 #include <linux/syscalls.h>
 #include <linux/sysctl.h>
@@ -2032,12 +2034,48 @@ static long seccomp_set_mode_filter(unsigned int flags,
 	seccomp_filter_free(prepared);
 	return ret;
 }
+
+static long seccomp_load_filter(const char __user *filter)
+{
+	struct sock_fprog fprog;
+	struct bpf_prog *prog;
+	int ret;
+
+	ret = seccomp_copy_user_filter(filter, &fprog);
+	if (ret)
+		return ret;
+
+	ret = seccomp_prepare_prog(&prog, &fprog);
+	if (ret)
+		return ret;
+
+	ret = security_bpf_prog_alloc(prog->aux);
+	if (ret) {
+		bpf_prog_free(prog);
+		return ret;
+	}
+
+	prog->aux->user = get_current_user();
+	atomic64_set(&prog->aux->refcnt, 1);
+	prog->type = BPF_PROG_TYPE_SECCOMP;
+
+	ret = bpf_prog_new_fd(prog);
+	if (ret < 0)
+		bpf_prog_put(prog);
+
+	return ret;
+}
 #else
 static inline long seccomp_set_mode_filter(unsigned int flags,
 					   const char __user *filter)
 {
 	return -EINVAL;
 }
+
+static inline long seccomp_load_filter(const char __user *filter)
+{
+	return -EINVAL;
+}
 #endif
 
 static long seccomp_get_action_avail(const char __user *uaction)
@@ -2099,6 +2137,11 @@ static long do_seccomp(unsigned int op, unsigned int flags,
 			return -EINVAL;
 
 		return seccomp_get_notif_sizes(uargs);
+	case SECCOMP_LOAD_FILTER:
+		if (flags != 0)
+			return -EINVAL;
+
+		return seccomp_load_filter(uargs);
 	default:
 		return -EINVAL;
 	}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 7ba61b75bc0e..61c80ffb1724 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -995,6 +995,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_LOOKUP,
 	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
 	BPF_PROG_TYPE_NETFILTER,
+	BPF_PROG_TYPE_SECCOMP,
 };
 
 enum bpf_attach_type {
-- 
2.34.1

