netdev - [PATCH bpf-next 4/7] bpf: prepare for builtin bpf program

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Message-Id: <20181207114431.18038-5-bjorn.topel@gmail.com>
Date:   Fri,  7 Dec 2018 12:44:28 +0100
From:   Björn Töpel <bjorn.topel@...il.com>
To:     bjorn.topel@...il.com, magnus.karlsson@...el.com,
        magnus.karlsson@...il.com, ast@...nel.org, daniel@...earbox.net,
        netdev@...r.kernel.org
Cc:     Björn Töpel <bjorn.topel@...el.com>,
        brouer@...hat.com, u9012063@...il.com, qi.z.zhang@...el.com
Subject: [PATCH bpf-next 4/7] bpf: prepare for builtin bpf program

From: Björn Töpel <bjorn.topel@...el.com>

Break up bpf_prog_load into one function that allocates, initializes
and verifies a bpf program, and one that allocates a file descriptor.

The former function will be used in a later commit to load a builtin
BPF program.

Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
---
 kernel/bpf/syscall.c | 59 ++++++++++++++++++++++++++------------------
 1 file changed, 35 insertions(+), 24 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index aa05aa38f4a8..ee1328625330 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1441,7 +1441,8 @@ bpf_prog_load_check_attach_type(enum bpf_prog_type prog_type,
 /* last field in 'union bpf_attr' used by this command */
 #define	BPF_PROG_LOAD_LAST_FIELD func_info_cnt
 
-static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
+static struct bpf_prog *__bpf_prog_load(union bpf_attr *attr,
+					union bpf_attr __user *uattr)
 {
 	enum bpf_prog_type type = attr->prog_type;
 	struct bpf_prog *prog;
@@ -1450,45 +1451,45 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 	bool is_gpl;
 
 	if (CHECK_ATTR(BPF_PROG_LOAD))
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	if (attr->prog_flags & ~(BPF_F_STRICT_ALIGNMENT | BPF_F_ANY_ALIGNMENT))
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
 	    (attr->prog_flags & BPF_F_ANY_ALIGNMENT) &&
 	    !capable(CAP_SYS_ADMIN))
-		return -EPERM;
+		return ERR_PTR(-EPERM);
 
 	/* copy eBPF program license from user space */
 	if (strncpy_from_user(license, u64_to_user_ptr(attr->license),
 			      sizeof(license) - 1) < 0)
-		return -EFAULT;
+		return ERR_PTR(-EFAULT);
 	license[sizeof(license) - 1] = 0;
 
 	/* eBPF programs must be GPL compatible to use GPL-ed functions */
 	is_gpl = license_is_gpl_compatible(license);
 
 	if (attr->insn_cnt == 0 || attr->insn_cnt > BPF_MAXINSNS)
-		return -E2BIG;
+		return ERR_PTR(-E2BIG);
 
 	if (type == BPF_PROG_TYPE_KPROBE &&
 	    attr->kern_version != LINUX_VERSION_CODE)
-		return -EINVAL;
+		return  ERR_PTR(-EINVAL);
 
 	if (type != BPF_PROG_TYPE_SOCKET_FILTER &&
 	    type != BPF_PROG_TYPE_CGROUP_SKB &&
 	    !capable(CAP_SYS_ADMIN))
-		return -EPERM;
+		return ERR_PTR(-EPERM);
 
 	bpf_prog_load_fixup_attach_type(attr);
 	if (bpf_prog_load_check_attach_type(type, attr->expected_attach_type))
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
 	/* plain bpf_prog allocation */
 	prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
 	if (!prog)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	prog->expected_attach_type = attr->expected_attach_type;
 
@@ -1544,20 +1545,8 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 	if (err)
 		goto free_used_maps;
 
-	err = bpf_prog_new_fd(prog);
-	if (err < 0) {
-		/* failed to allocate fd.
-		 * bpf_prog_put() is needed because the above
-		 * bpf_prog_alloc_id() has published the prog
-		 * to the userspace and the userspace may
-		 * have refcnt-ed it through BPF_PROG_GET_FD_BY_ID.
-		 */
-		bpf_prog_put(prog);
-		return err;
-	}
-
 	bpf_prog_kallsyms_add(prog);
-	return err;
+	return prog;
 
 free_used_maps:
 	kvfree(prog->aux->func_info);
@@ -1570,7 +1559,29 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 	security_bpf_prog_free(prog->aux);
 free_prog_nouncharge:
 	bpf_prog_free(prog);
-	return err;
+	return ERR_PTR(err);
+}
+
+static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
+{
+	struct bpf_prog *prog = __bpf_prog_load(attr, uattr);
+	int fd;
+
+	if (IS_ERR(prog))
+		return PTR_ERR(prog);
+
+	fd = bpf_prog_new_fd(prog);
+	if (fd < 0) {
+		/* failed to allocate fd.
+		 * bpf_prog_put() is needed because the above
+		 * bpf_prog_alloc_id() has published the prog
+		 * to the userspace and the userspace may
+		 * have refcnt-ed it through BPF_PROG_GET_FD_BY_ID.
+		 */
+		bpf_prog_put(prog);
+	}
+
+	return fd;
 }
 
 #define BPF_OBJ_LAST_FIELD file_flags
-- 
2.19.1