netdev - [PATCH 13/18] bpf-preload: Move pinned links and maps to a dedicated directory in bpffs

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Date:   Mon, 28 Mar 2022 19:50:28 +0200
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     <corbet@....net>, <viro@...iv.linux.org.uk>, <ast@...nel.org>,
        <daniel@...earbox.net>, <andrii@...nel.org>, <kpsingh@...nel.org>,
        <shuah@...nel.org>, <mcoquelin.stm32@...il.com>,
        <alexandre.torgue@...s.st.com>, <zohar@...ux.ibm.com>
CC:     <linux-doc@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
        <linux-kselftest@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-integrity@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH 13/18] bpf-preload: Move pinned links and maps to a dedicated directory in bpffs

With support for preloading multiple eBPF programs, any map, link or prog
will appear in the bpf filesystem. To identify which eBPF program a pinned
object belongs to, create a subdir for each eBPF program preloaded and
place the pinned object in the new subdir.

Keep the pinned objects of iterators_bpf in the root directory of bpffs,
for compatibility reasons.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 kernel/bpf/inode.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 440ea517cc29..619cdef0ba54 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -740,9 +740,30 @@ static bool bpf_preload_list_mod_get(void)
 	return ret;
 }
 
+static struct dentry *create_subdir(struct dentry *parent, const char *name)
+{
+	struct dentry *dentry;
+	int err;
+
+	inode_lock(parent->d_inode);
+	dentry = lookup_one_len(name, parent, strlen(name));
+	if (IS_ERR(dentry))
+		goto out;
+
+	err = vfs_mkdir(&init_user_ns, parent->d_inode, dentry, 0755);
+	if (err) {
+		dput(dentry);
+		dentry = ERR_PTR(err);
+	}
+out:
+	inode_unlock(parent->d_inode);
+	return dentry;
+}
+
 static int bpf_preload_list(struct dentry *parent)
 {
 	struct bpf_preload_ops_item *cur;
+	struct dentry *cur_parent;
 	int err;
 
 	if (bpf_preload_ops) {
@@ -755,7 +776,19 @@ static int bpf_preload_list(struct dentry *parent)
 		if (!cur->ops)
 			continue;
 
-		err = cur->ops->preload(parent);
+		cur_parent = parent;
+
+		if (strcmp(cur->obj_name, "bpf_preload")) {
+			cur_parent = create_subdir(parent, cur->obj_name);
+			if (IS_ERR(cur_parent))
+				cur_parent = parent;
+		}
+
+		err = cur->ops->preload(cur_parent);
+
+		if (cur_parent != parent)
+			dput(cur_parent);
+
 		if (err)
 			return err;
 	}
-- 
2.32.0