From cc4f3b5a6ab4693aba94a45cc073188df4d67175 Mon Sep 17 00:00:00 2001 From: Namjae Jeon Date: Mon, 26 Dec 2022 01:28:52 +0900 Subject: ksmbd: fix infinite loop in ksmbd_conn_handler_loop() If kernel_recvmsg() return -EAGAIN in ksmbd_tcp_readv() and go round again, It will cause infinite loop issue. And all threads from next connections would be doing that. This patch add max retry count(2) to avoid it. kernel_recvmsg() will wait during 7sec timeout and try to retry two time if -EAGAIN is returned. And add flags of kvmalloc to __GFP_NOWARN and __GFP_NORETRY to disconnect immediately without retrying on memory alloation failure. Fixes: 0626e66 ("cifsd: add server handler for central processing and tranport layers") Cc: stable@vger.kernel.org Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-18259 Reviewed-by: Sergey Senozhatsky Signed-off-by: Namjae Jeon --- connection.c | 7 +++++-- transport_tcp.c | 5 ++++- 2 files changed, 9 insertions(+), 3 deletions(-) --- a/connection.c +++ b/connection.c @@ -337,9 +337,12 @@ int ksmbd_conn_handler_loop(void *p) /* 4 for rfc1002 length field */ size = pdu_size + 4; - conn->request_buf = kvmalloc(size, GFP_KERNEL); + conn->request_buf = kvmalloc(size, + GFP_KERNEL | + __GFP_NOWARN | + __GFP_NORETRY); if (!conn->request_buf) - continue; + break; memcpy(conn->request_buf, hdr_buf, sizeof(hdr_buf)); if (!ksmbd_smb_request(conn)) --- a/transport_tcp.c +++ b/transport_tcp.c @@ -323,6 +323,7 @@ static int ksmbd_tcp_readv(struct tcp_tr struct msghdr ksmbd_msg; struct kvec *iov; struct ksmbd_conn *conn = KSMBD_TRANS(t)->conn; + int max_retry = 2; iov = get_conn_iovec(t, nr_segs); if (!iov) @@ -349,9 +350,11 @@ static int ksmbd_tcp_readv(struct tcp_tr } else if (conn->status == KSMBD_SESS_NEED_RECONNECT) { total_read = -EAGAIN; break; - } else if (length == -ERESTARTSYS || length == -EAGAIN) { + } else if ((length == -ERESTARTSYS || length == -EAGAIN) && + max_retry) { usleep_range(1000, 2000); length = 0; + max_retry--; continue; } else if (length <= 0) { total_read = -EAGAIN;