linux-kernel - [PATCH bpf 1/1] bpf: test_run: fix ctx leak in bpf_prog_test_run

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Message-Id: <20251014120037.1981316-1-shardulsb08@gmail.com>
Date: Tue, 14 Oct 2025 17:30:37 +0530
From: Shardul Bankar <shardulsb08@...il.com>
To: bpf@...r.kernel.org
Cc: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	netdev@...r.kernel.org (open list:NETWORKING [GENERAL]),
	linux-kernel@...r.kernel.org (open list),
	Shardul Bankar <shardulsb08@...il.com>
Subject: [PATCH bpf 1/1] bpf: test_run: fix ctx leak in bpf_prog_test_run_xdp error path

Fix a memory leak in bpf_prog_test_run_xdp() where the context buffer
allocated by bpf_ctx_init() is not freed when the function returns early
due to a data size check.

On the failing path:
  ctx = bpf_ctx_init(...);
  if (kattr->test.data_size_in - meta_sz < ETH_HLEN)
      return -EINVAL;

The early return bypasses the cleanup label that kfree()s ctx, leading to a
leak detectable by kmemleak under fuzzing. Change the return to jump to the
existing free_ctx label.

Fixes: fe9544ed1a2e ("bpf: Support specifying linear xdp packet data size for BPF_PROG_TEST_RUN")
Reported-by: BPF Runtime Fuzzer (BRF)
Signed-off-by: Shardul Bankar <shardulsb08@...il.com>
---
 net/bpf/test_run.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index dfb03ee0bb62..1782e83de2cb 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -1269,7 +1269,7 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
 		goto free_ctx;
 
 	if (kattr->test.data_size_in - meta_sz < ETH_HLEN)
-		return -EINVAL;
+		goto free_ctx;
 
 	data = bpf_test_init(kattr, linear_sz, max_linear_sz, headroom, tailroom);
 	if (IS_ERR(data)) {
-- 
2.34.1