linux-hardening - [PATCH bpf-next v2 1/3] bpf/verifier: Fix potential memory leak in array reallocation

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Date:   Fri, 28 Oct 2022 19:54:30 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Alexei Starovoitov <ast@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: [PATCH bpf-next v2 1/3] bpf/verifier: Fix potential memory leak in array reallocation

If an error (NULL) is returned by krealloc(), callers of realloc_array()
were setting their allocation pointers to NULL, but on error krealloc()
does not touch the original allocation. This would result in a memory
resource leak. Instead, free the old allocation on the error handling
path.

Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: John Fastabend <john.fastabend@...il.com>
Cc: Andrii Nakryiko <andrii@...nel.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Song Liu <song@...nel.org>
Cc: Yonghong Song <yhs@...com>
Cc: KP Singh <kpsingh@...nel.org>
Cc: Stanislav Fomichev <sdf@...gle.com>
Cc: Hao Luo <haoluo@...gle.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: bpf@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 kernel/bpf/verifier.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 014ee0953dbd..eb8c34db74c7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1027,12 +1027,17 @@ static void *copy_array(void *dst, const void *src, size_t n, size_t size, gfp_t
  */
 static void *realloc_array(void *arr, size_t old_n, size_t new_n, size_t size)
 {
+	void *new_arr;
+
 	if (!new_n || old_n == new_n)
 		goto out;
 
-	arr = krealloc_array(arr, new_n, size, GFP_KERNEL);
-	if (!arr)
+	new_arr = krealloc_array(arr, new_n, size, GFP_KERNEL);
+	if (!new_arr) {
+		kfree(arr);
 		return NULL;
+	}
+	arr = new_arr;
 
 	if (new_n > old_n)
 		memset(arr + old_n * size, 0, (new_n - old_n) * size);
-- 
2.34.1