From: Pengpeng Hou Date: Sun, 5 Apr 2026 00:40:00 +0000 (+0800) Subject: nfc: pn533: allocate rx skb before consuming bytes X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c71ba669b570c7b3f86ec875be222ea11dacb352;p=thirdparty%2Fkernel%2Flinux.git 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: c656aa4c27b1 ("nfc: pn533: add UART phy driver") Cc: stable@vger.kernel.org Signed-off-by: Pengpeng Hou Link: https://patch.msgid.link/20260405094003.3-pn533-v2-pengpeng@iscas.ac.cn Signed-off-by: Paolo Abeni --- diff --git a/drivers/nfc/pn533/uart.c b/drivers/nfc/pn533/uart.c index 1b82b7b2a5fa..e0d67cd2ac9b 100644 --- a/drivers/nfc/pn533/uart.c +++ b/drivers/nfc/pn533/uart.c @@ -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;