linux-kernel - [PATCH v1 1/3] perf bpf-event: Fix use-after-free in synthesis

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Message-ID: <20250902181713.309797-2-irogers@google.com>
Date: Tue,  2 Sep 2025 11:17:11 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, Blake Jones <blakejones@...gle.com>, 
	Zhongqiu Han <quic_zhonhan@...cinc.com>, Andrii Nakryiko <andrii@...nel.org>, 
	Song Liu <songliubraving@...com>, Dave Marchevsky <davemarchevsky@...com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org, Howard Chu <howardchu95@...il.com>, song@...nel.org, 
	Yonghong Song <yonghong.song@...ux.dev>
Subject: [PATCH v1 1/3] perf bpf-event: Fix use-after-free in synthesis

Calls to perf_env__insert_bpf_prog_info may fail as a sideband thread
may already have inserted the bpf_prog_info. Such failures may yield
info_linear being freed which then causes use-after-free issues with
the internal bpf_prog_info info struct. Make it so that
perf_env__insert_bpf_prog_info trigger early non-error paths and fix
the use-after-free in perf_event__synthesize_one_bpf_prog. Add proper
return error handling to perf_env__add_bpf_info (that calls
perf_env__insert_bpf_prog_info) and propagate the return value in its
callers.

Closes: https://lore.kernel.org/lkml/CAP-5=fWJQcmUOP7MuCA2ihKnDAHUCOBLkQFEkQES-1ZZTrgf8Q@mail.gmail.com/
Fixes: 03edb7020bb9 ("perf bpf: Fix two memory leakages when calling perf_env__insert_bpf_prog_info()")
Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/bpf-event.c | 39 +++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
index 5b6d3e899e11..2298cd396c42 100644
--- a/tools/perf/util/bpf-event.c
+++ b/tools/perf/util/bpf-event.c
@@ -657,9 +657,15 @@ static int perf_event__synthesize_one_bpf_prog(struct perf_session *session,
 		info_node->info_linear = info_linear;
 		info_node->metadata = NULL;
 		if (!perf_env__insert_bpf_prog_info(env, info_node)) {
-			free(info_linear);
+			/*
+			 * Insert failed, likely because of a duplicate event
+			 * made by the sideband thread. Ignore synthesizing the
+			 * metadata.
+			 */
 			free(info_node);
+			goto out;
 		}
+		/* info_linear is now owned by info_node and shouldn't be freed below. */
 		info_linear = NULL;
 
 		/*
@@ -827,18 +833,18 @@ int perf_event__synthesize_bpf_events(struct perf_session *session,
 	return err;
 }
 
-static void perf_env__add_bpf_info(struct perf_env *env, u32 id)
+static int perf_env__add_bpf_info(struct perf_env *env, u32 id)
 {
 	struct bpf_prog_info_node *info_node;
 	struct perf_bpil *info_linear;
 	struct btf *btf = NULL;
 	u64 arrays;
 	u32 btf_id;
-	int fd;
+	int fd, err = 0;
 
 	fd = bpf_prog_get_fd_by_id(id);
 	if (fd < 0)
-		return;
+		return -EINVAL;
 
 	arrays = 1UL << PERF_BPIL_JITED_KSYMS;
 	arrays |= 1UL << PERF_BPIL_JITED_FUNC_LENS;
@@ -852,6 +858,7 @@ static void perf_env__add_bpf_info(struct perf_env *env, u32 id)
 	info_linear = get_bpf_prog_info_linear(fd, arrays);
 	if (IS_ERR_OR_NULL(info_linear)) {
 		pr_debug("%s: failed to get BPF program info. aborting\n", __func__);
+		err = PTR_ERR(info_linear);
 		goto out;
 	}
 
@@ -862,38 +869,46 @@ static void perf_env__add_bpf_info(struct perf_env *env, u32 id)
 		info_node->info_linear = info_linear;
 		info_node->metadata = bpf_metadata_create(&info_linear->info);
 		if (!perf_env__insert_bpf_prog_info(env, info_node)) {
+			pr_debug("%s: duplicate add bpf info request for id %u\n",
+				 __func__, btf_id);
 			free(info_linear);
 			free(info_node);
+			goto out;
 		}
-	} else
+	} else {
 		free(info_linear);
+		err = -ENOMEM;
+		goto out;
+	}
 
 	if (btf_id == 0)
 		goto out;
 
 	btf = btf__load_from_kernel_by_id(btf_id);
-	if (libbpf_get_error(btf)) {
-		pr_debug("%s: failed to get BTF of id %u, aborting\n",
-			 __func__, btf_id);
-		goto out;
+	if (!btf) {
+		err = -errno;
+		pr_debug("%s: failed to get BTF of id %u %d\n", __func__, btf_id, err);
+	} else {
+		perf_env__fetch_btf(env, btf_id, btf);
 	}
-	perf_env__fetch_btf(env, btf_id, btf);
 
 out:
 	btf__free(btf);
 	close(fd);
+	return err;
 }
 
 static int bpf_event__sb_cb(union perf_event *event, void *data)
 {
 	struct perf_env *env = data;
+	int ret = 0;
 
 	if (event->header.type != PERF_RECORD_BPF_EVENT)
 		return -1;
 
 	switch (event->bpf.type) {
 	case PERF_BPF_EVENT_PROG_LOAD:
-		perf_env__add_bpf_info(env, event->bpf.id);
+		ret = perf_env__add_bpf_info(env, event->bpf.id);
 
 	case PERF_BPF_EVENT_PROG_UNLOAD:
 		/*
@@ -907,7 +922,7 @@ static int bpf_event__sb_cb(union perf_event *event, void *data)
 		break;
 	}
 
-	return 0;
+	return ret;
 }
 
 int evlist__add_bpf_sb_event(struct evlist *evlist, struct perf_env *env)
-- 
2.51.0.355.g5224444f11-goog