net: nfc: nci: fix a possible sleep-in-atomic-context bug in nci_uart_tty_receive()

[ Upstream commit b7ac893652cafadcf669f78452329727e4e255cc ]

The kernel may sleep while holding a spinlock.
The function call path (from bottom to top) in Linux 4.19 is:

net/nfc/nci/uart.c, 349:
	nci_skb_alloc in nci_uart_default_recv_buf
net/nfc/nci/uart.c, 255:
	(FUNC_PTR)nci_uart_default_recv_buf in nci_uart_tty_receive
net/nfc/nci/uart.c, 254:
	spin_lock in nci_uart_tty_receive

nci_skb_alloc(GFP_KERNEL) can sleep at runtime.
(FUNC_PTR) means a function pointer is called.

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC for
nci_skb_alloc().

This bug is found by a static analysis tool STCheck written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/nfc/nci/uart.c b/net/nfc/nci/uart.c
index 21d8875..c3f2faa 100644 (file)
--- a/net/nfc/nci/uart.c
+++ b/net/nfc/nci/uart.c
@@ -355,7 +355,7 @@ static int nci_uart_default_recv_buf(struct nci_uart *nu, const u8 *data,
                        nu->rx_packet_len = -1;
                        nu->rx_skb = nci_skb_alloc(nu->ndev,
                                                   NCI_MAX_PACKET_SIZE,
-                                                  GFP_KERNEL);
+                                                  GFP_ATOMIC);
                        if (!nu->rx_skb)
                                return -ENOMEM;
                }