netdev - [PATCH v4 3/3] libbpf: cleanup the legacy uprobe_event on failed add/attach

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Date:   Wed, 29 Jun 2022 23:18:47 +0800
From:   Chuang Wang <nashuiliang@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Chuang Wang <nashuiliang@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 3/3] libbpf: cleanup the legacy uprobe_event on failed add/attach_event()

A potential scenario, when an error is returned after
add_uprobe_event_legacy() in perf_event_uprobe_open_legacy(), or
bpf_program__attach_perf_event_opts() in
bpf_program__attach_uprobe_opts() returns an error, the uprobe_event
that was previously created is not cleaned.

So, with this patch, when an error is returned, fix this by adding
remove_uprobe_event_legacy()

Signed-off-by: Chuang Wang <nashuiliang@...il.com>
---
 tools/lib/bpf/libbpf.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 159b69d8b941..5aa6033a0284 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10240,9 +10240,10 @@ static int perf_event_uprobe_open_legacy(const char *probe_name, bool retprobe,
 	}
 	type = determine_uprobe_perf_type_legacy(probe_name, retprobe);
 	if (type < 0) {
+		err = type;
 		pr_warn("failed to determine legacy uprobe event id for %s:0x%zx: %d\n",
-			binary_path, offset, type);
-		return type;
+			binary_path, offset, err);
+		goto err_clean_legacy;
 	}
 
 	memset(&attr, 0, sizeof(attr));
@@ -10257,9 +10258,14 @@ static int perf_event_uprobe_open_legacy(const char *probe_name, bool retprobe,
 	if (pfd < 0) {
 		err = -errno;
 		pr_warn("legacy uprobe perf_event_open() failed: %d\n", err);
-		return err;
+		goto err_clean_legacy;
 	}
 	return pfd;
+
+err_clean_legacy:
+	/* Clear the newly added legacy uprobe_event */
+	remove_uprobe_event_legacy(probe_name, retprobe);
+	return err;
 }
 
 /* Return next ELF section of sh_type after scn, or first of that type if scn is NULL. */
@@ -10593,7 +10599,7 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
 			prog->name, retprobe ? "uretprobe" : "uprobe",
 			binary_path, func_offset,
 			libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
-		goto err_out;
+		goto err_clean_legacy;
 	}
 	if (legacy) {
 		struct bpf_link_perf *perf_link = container_of(link, struct bpf_link_perf, link);
@@ -10603,10 +10609,14 @@ bpf_program__attach_uprobe_opts(const struct bpf_program *prog, pid_t pid,
 		perf_link->legacy_is_retprobe = retprobe;
 	}
 	return link;
+
+err_clean_legacy:
+	if (legacy)
+		remove_uprobe_event_legacy(legacy_probe, retprobe);
+
 err_out:
 	free(legacy_probe);
 	return libbpf_err_ptr(err);
-
 }
 
 /* Format of u[ret]probe section definition supporting auto-attach:
-- 
2.34.1