From: Namjae Jeon linkinjeon@kernel.org
commit 83dcedd5540d4ac61376ddff5362f7d9f866a6ec upstream.
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: 0626e6641f6b ("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 senozhatsky@chromium.org Signed-off-by: Namjae Jeon linkinjeon@kernel.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ksmbd/connection.c | 7 +++++-- fs/ksmbd/transport_tcp.c | 5 ++++- 2 files changed, 9 insertions(+), 3 deletions(-)
--- a/fs/ksmbd/connection.c +++ b/fs/ksmbd/connection.c @@ -310,9 +310,12 @@ 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/fs/ksmbd/transport_tcp.c +++ b/fs/ksmbd/transport_tcp.c @@ -295,6 +295,7 @@ 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) @@ -321,9 +322,11 @@ 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;