netdev - [PATCH net v2] net/tls: do not free tls_rec on async operation in bpf_exec_tx

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Date: Sat, 9 Sep 2023 16:14:34 +0800
From: Liu Jian <liujian56@...wei.com>
To: <borisp@...dia.com>, <john.fastabend@...il.com>, <kuba@...nel.org>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <pabeni@...hat.com>,
	<vfedorenko@...ek.ru>, <sd@...asysnail.net>, <netdev@...r.kernel.org>
CC: <liujian56@...wei.com>
Subject: [PATCH net v2] net/tls: do not free tls_rec on async operation in bpf_exec_tx_verdict()

I got the below warning when do fuzzing test:
BUG: KASAN: null-ptr-deref in scatterwalk_copychunks+0x320/0x470
Read of size 4 at addr 0000000000000008 by task kworker/u8:1/9

CPU: 0 PID: 9 Comm: kworker/u8:1 Tainted: G           OE
Hardware name: linux,dummy-virt (DT)
Workqueue: pencrypt_parallel padata_parallel_worker
Call trace:
 dump_backtrace+0x0/0x420
 show_stack+0x34/0x44
 dump_stack+0x1d0/0x248
 __kasan_report+0x138/0x140
 kasan_report+0x44/0x6c
 __asan_load4+0x94/0xd0
 scatterwalk_copychunks+0x320/0x470
 skcipher_next_slow+0x14c/0x290
 skcipher_walk_next+0x2fc/0x480
 skcipher_walk_first+0x9c/0x110
 skcipher_walk_aead_common+0x380/0x440
 skcipher_walk_aead_encrypt+0x54/0x70
 ccm_encrypt+0x13c/0x4d0
 crypto_aead_encrypt+0x7c/0xfc
 pcrypt_aead_enc+0x28/0x84
 padata_parallel_worker+0xd0/0x2dc
 process_one_work+0x49c/0xbdc
 worker_thread+0x124/0x880
 kthread+0x210/0x260
 ret_from_fork+0x10/0x18

This is because the value of rec_seq of tls_crypto_info configured by the
user program is too large, for example, 0xffffffffffffff. In addition, TLS
is asynchronously accelerated. When tls_do_encryption() returns
-EINPROGRESS and sk->sk_err is set to EBADMSG due to rec_seq overflow,
skmsg is released before the asynchronous encryption process ends. As a
result, the UAF problem occurs during the asynchronous processing of the
encryption module.

If the operation is asynchronous and the encryption module returns
EINPROGRESS, do not free the record information.

Fixes: 635d93981786 ("net/tls: free record only on encryption error")
Signed-off-by: Liu Jian <liujian56@...wei.com>
---
v1->v2:
  Retain the current EBADMSG error info and add error handling.
 net/tls/tls_sw.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 1ed4a611631f..d1fc295b83b5 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -817,7 +817,7 @@ static int bpf_exec_tx_verdict(struct sk_msg *msg, struct sock *sk,
 	psock = sk_psock_get(sk);
 	if (!psock || !policy) {
 		err = tls_push_record(sk, flags, record_type);
-		if (err && sk->sk_err == EBADMSG) {
+		if (err && err != -EINPROGRESS && sk->sk_err == EBADMSG) {
 			*copied -= sk_msg_free(sk, msg);
 			tls_free_open_rec(sk);
 			err = -sk->sk_err;
@@ -846,7 +846,7 @@ static int bpf_exec_tx_verdict(struct sk_msg *msg, struct sock *sk,
 	switch (psock->eval) {
 	case __SK_PASS:
 		err = tls_push_record(sk, flags, record_type);
-		if (err && sk->sk_err == EBADMSG) {
+		if (err && err != -EINPROGRESS && sk->sk_err == EBADMSG) {
 			*copied -= sk_msg_free(sk, msg);
 			tls_free_open_rec(sk);
 			err = -sk->sk_err;
-- 
2.34.1