netdev - [PATCH bpf-next] libbpf: fix memory leak when emitting final btf

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Date:   Fri, 26 Mar 2021 21:25:02 -0700
From:   Andrii Nakryiko <andrii@...nel.org>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii@...nel.org>, <kernel-team@...com>
Subject: [PATCH bpf-next] libbpf: fix memory leak when emitting final btf_ext

Free temporary allocated memory used to construct finalized .BTF.ext data.
Found by Coverity static analysis on libbpf's Github repo.

Fixes: 8fd27bf69b86 ("libbpf: Add BPF static linker BTF and BTF.ext support")
Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
---
 tools/lib/bpf/linker.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index a29d62ff8041..46b16cbdcda3 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -1906,8 +1906,10 @@ static int finalize_btf_ext(struct bpf_linker *linker)
 			struct dst_sec *sec = &linker->secs[i];
 
 			sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->func_info);
-			if (sz < 0)
-				return sz;
+			if (sz < 0) {
+				err = sz;
+				goto out;
+			}
 
 			cur += sz;
 		}
@@ -1921,8 +1923,10 @@ static int finalize_btf_ext(struct bpf_linker *linker)
 			struct dst_sec *sec = &linker->secs[i];
 
 			sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->line_info);
-			if (sz < 0)
-				return sz;
+			if (sz < 0) {
+				err = sz;
+				goto out;
+			}
 
 			cur += sz;
 		}
@@ -1936,8 +1940,10 @@ static int finalize_btf_ext(struct bpf_linker *linker)
 			struct dst_sec *sec = &linker->secs[i];
 
 			sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->core_relo_info);
-			if (sz < 0)
-				return sz;
+			if (sz < 0) {
+				err = sz;
+				goto out;
+			}
 
 			cur += sz;
 		}
@@ -1948,8 +1954,10 @@ static int finalize_btf_ext(struct bpf_linker *linker)
 	if (err) {
 		linker->btf_ext = NULL;
 		pr_warn("failed to parse final .BTF.ext data: %d\n", err);
-		return err;
+		goto out;
 	}
 
-	return 0;
+out:
+	free(data);
+	return err;
 }
-- 
2.30.2