linux-kernel - [PATCH 3/5] bpf: Improve exception handling in bpf_core

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Date: Sat, 30 Dec 2023 21:10:20 +0100
From: Markus Elfring <Markus.Elfring@....de>
To: bpf@...r.kernel.org, netdev@...r.kernel.org,
 kernel-janitors@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
 Andrii Nakryiko <andrii@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
 Stanislav Fomichev <sdf@...gle.com>, Yonghong Song <yonghong.song@...ux.dev>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 3/5] bpf: Improve exception handling in bpf_core_apply()

From: Markus Elfring <elfring@...rs.sourceforge.net>
Date: Sat, 30 Dec 2023 19:28:25 +0100

The kfree() function was called in two cases by
the bpf_core_apply() function during error handling
even if the passed data structure member contained a null pointer.
This issue was detected by using the Coccinelle software.

* Thus use another label.

* Reorder function calls at the end.

Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
---
 kernel/bpf/btf.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 51e8b4bee0c8..e8391025d408 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -8322,13 +8322,13 @@ int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
 			bpf_log(ctx->log, "target candidate search failed for %d\n",
 				relo->type_id);
 			err = PTR_ERR(cc);
-			goto out;
+			goto unlock_mutex;
 		}
 		if (cc->cnt) {
 			cands.cands = kcalloc(cc->cnt, sizeof(*cands.cands), GFP_KERNEL);
 			if (!cands.cands) {
 				err = -ENOMEM;
-				goto out;
+				goto unlock_mutex;
 			}
 		}
 		for (i = 0; i < cc->cnt; i++) {
@@ -8355,13 +8355,15 @@ int bpf_core_apply(struct bpf_core_ctx *ctx, const struct bpf_core_relo *relo,
 				  &targ_res);

 out:
-	kfree(specs);
 	if (need_cands) {
 		kfree(cands.cands);
+unlock_mutex:
 		mutex_unlock(&cand_cache_mutex);
 		if (ctx->log->level & BPF_LOG_LEVEL2)
 			print_cand_cache(ctx->log);
 	}
+
+	kfree(specs);
 	return err;
 }

--
2.43.0