netdev - [PATCH net] tls: do not return error when the tls_bigint overflows in tls_advance_record

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Date: Wed, 6 Sep 2023 14:52:37 +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>, <netdev@...r.kernel.org>
CC: <liujian56@...wei.com>
Subject: [PATCH net] tls: do not return error when the tls_bigint overflows in tls_advance_record_sn()

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.

I didn't see the rec_seq overflow causing other problems, so let's get rid
of the overflow error here.

Fixes: 635d93981786 ("net/tls: free record only on encryption error")
Signed-off-by: Liu Jian <liujian56@...wei.com>
---
 net/tls/tls.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/tls/tls.h b/net/tls/tls.h
index 28a8c0e80e3c..3f0e10df8053 100644
--- a/net/tls/tls.h
+++ b/net/tls/tls.h
@@ -304,8 +304,7 @@ static inline void
 tls_advance_record_sn(struct sock *sk, struct tls_prot_info *prot,
 		      struct cipher_context *ctx)
 {
-	if (tls_bigint_increment(ctx->rec_seq, prot->rec_seq_size))
-		tls_err_abort(sk, -EBADMSG);
+	tls_bigint_increment(ctx->rec_seq, prot->rec_seq_size);
 
 	if (prot->version != TLS_1_3_VERSION &&
 	    prot->cipher_type != TLS_CIPHER_CHACHA20_POLY1305)
-- 
2.34.1