netdev - [PATCH bpf-next] bpf: fix memory leak in grow_stack

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Date:   Mon, 31 Oct 2022 15:08:12 +0800
From:   Zhengchao Shao <shaozhengchao@...wei.com>
To:     <netdev@...r.kernel.org>, <bpf@...r.kernel.org>, <ast@...nel.org>,
        <daniel@...earbox.net>
CC:     <john.fastabend@...il.com>, <andrii@...nel.org>,
        <martin.lau@...ux.dev>, <song@...nel.org>, <yhs@...com>,
        <kpsingh@...nel.org>, <sdf@...gle.com>, <haoluo@...gle.com>,
        <jolsa@...nel.org>, <lmb@...udflare.com>, <weiyongjun1@...wei.com>,
        <yuehaibing@...wei.com>, <shaozhengchao@...wei.com>
Subject: [PATCH bpf-next] bpf: fix memory leak in grow_stack_state()

The realloc_array() fails, but the previous memory is not released.
However, state->stack and state->refs are set to NULL. This will
cause memory leakage.

The memory leak information is as follows:
unreferenced object 0xffff888019801800 (size 256):
  comm "bpf_repo", pid 6490, jiffies 4294959200 (age 17.170s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000b211474b>] __kmalloc_node_track_caller+0x45/0xc0
    [<0000000086712a0b>] krealloc+0x83/0xd0
    [<00000000139aab02>] realloc_array+0x82/0xe2
    [<00000000b1ca41d1>] grow_stack_state+0xfb/0x186
    [<00000000cd6f36d2>] check_mem_access.cold+0x141/0x1341
    [<0000000081780455>] do_check_common+0x5358/0xb350
    [<0000000015f6b091>] bpf_check.cold+0xc3/0x29d
    [<000000002973c690>] bpf_prog_load+0x13db/0x2240
    [<00000000028d1644>] __sys_bpf+0x1605/0x4ce0
    [<00000000053f29bd>] __x64_sys_bpf+0x75/0xb0
    [<0000000056fedaf5>] do_syscall_64+0x35/0x80
    [<000000002bd58261>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: c69431aab67a ("bpf: verifier: Improve function state reallocation")
Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
---
 kernel/bpf/verifier.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7f0a9f6cb889..c0b0cc2891e3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1027,12 +1027,16 @@ 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 *old_arr = arr;
+
 	if (!new_n || old_n == new_n)
 		goto out;
 
 	arr = krealloc_array(arr, new_n, size, GFP_KERNEL);
-	if (!arr)
+	if (!arr) {
+		kfree(old_arr);
 		return NULL;
+	}
 
 	if (new_n > old_n)
 		memset(arr + old_n * size, 0, (new_n - old_n) * size);
-- 
2.17.1