Commit c71ba669 authored by Pengpeng Hou's avatar Pengpeng Hou Committed by Paolo Abeni
Browse files

nfc: pn533: allocate rx skb before consuming bytes 



pn532_receive_buf() reports the number of accepted bytes to the serdev
core. The current code consumes bytes into recv_skb and may already hand
a complete frame to pn533_recv_frame() before allocating a fresh receive
buffer.

If that alloc_skb() fails, the callback returns 0 even though it has
already consumed bytes, and it leaves recv_skb as NULL for the next
receive callback. That breaks the receive_buf() accounting contract and
can also lead to a NULL dereference on the next skb_put_u8().

Allocate the receive skb lazily before consuming the next byte instead.
If allocation fails, return the number of bytes already accepted.

Fixes: c656aa4c ("nfc: pn533: add UART phy driver")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPengpeng Hou <pengpeng@iscas.ac.cn>
Link: https://patch.msgid.link/20260405094003.3-pn533-v2-pengpeng@iscas.ac.cn


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent ebe560ea

drivers/nfc/pn533/uart.c

+8 −3
Original line number Diff line number Diff line
@@ -211,6 +211,13 @@ static size_t pn532_receive_buf(struct serdev_device *serdev, 


	timer_delete(&dev->cmd_timeout);

	for (i = 0; i < count; i++) {

		if (!dev->recv_skb) {

			dev->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN,

						  GFP_KERNEL);

			if (!dev->recv_skb)

				return i;

		}



		if (unlikely(!skb_tailroom(dev->recv_skb)))

			skb_trim(dev->recv_skb, 0);
@@ -219,9 +226,7 @@ static size_t pn532_receive_buf(struct serdev_device *serdev, 
			continue;



		pn533_recv_frame(dev->priv, dev->recv_skb, 0);

		dev->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN, GFP_KERNEL);

		if (!dev->recv_skb)

			return 0;

		dev->recv_skb = NULL;

	}



	return i;