netdev - [PATCH bpf-next] libbpf: fix memory leak and optimize BTF sanitization

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Date:   Thu, 9 Jul 2020 18:10:23 -0700
From:   Andrii Nakryiko <andriin@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii.nakryiko@...il.com>, <kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf-next] libbpf: fix memory leak and optimize BTF sanitization

Coverity's static analysis helpfully reported a memory leak introduced by
0f0e55d8247c ("libbpf: Improve BTF sanitization handling"). While fixing it,
I realized that btf__new() already creates a memory copy, so there is no need
to do this. So this patch also fixes misleading btf__new() signature to make
data into a `const void *` input parameter. And it avoids unnecessary memory
allocation and copy in BTF sanitization code altogether.

Fixes: 0f0e55d8247c ("libbpf: Improve BTF sanitization handling")
Signed-off-by: Andrii Nakryiko <andriin@...com>
---
 tools/lib/bpf/btf.c    |  2 +-
 tools/lib/bpf/btf.h    |  2 +-
 tools/lib/bpf/libbpf.c | 11 +++--------
 3 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index c8861c9e3635..c9e760e120dc 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -397,7 +397,7 @@ void btf__free(struct btf *btf)
 	free(btf);
 }
 
-struct btf *btf__new(__u8 *data, __u32 size)
+struct btf *btf__new(const void *data, __u32 size)
 {
 	struct btf *btf;
 	int err;
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 173eff23c472..a3b7ef9b737f 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -63,7 +63,7 @@ struct btf_ext_header {
 };
 
 LIBBPF_API void btf__free(struct btf *btf);
-LIBBPF_API struct btf *btf__new(__u8 *data, __u32 size);
+LIBBPF_API struct btf *btf__new(const void *data, __u32 size);
 LIBBPF_API struct btf *btf__parse_elf(const char *path,
 				      struct btf_ext **btf_ext);
 LIBBPF_API int btf__finalize_data(struct bpf_object *obj, struct btf *btf);
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 6602eb479596..25e4f77be8d7 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2533,17 +2533,12 @@ static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
 
 	sanitize = btf_needs_sanitization(obj);
 	if (sanitize) {
-		const void *orig_data;
-		void *san_data;
+		const void *raw_data;
 		__u32 sz;
 
 		/* clone BTF to sanitize a copy and leave the original intact */
-		orig_data = btf__get_raw_data(obj->btf, &sz);
-		san_data = malloc(sz);
-		if (!san_data)
-			return -ENOMEM;
-		memcpy(san_data, orig_data, sz);
-		kern_btf = btf__new(san_data, sz);
+		raw_data = btf__get_raw_data(obj->btf, &sz);
+		kern_btf = btf__new(raw_data, sz);
 		if (IS_ERR(kern_btf))
 			return PTR_ERR(kern_btf);
 
-- 
2.24.1