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nfc: pn533: allocate rx skb before consuming bytes

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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: c656aa4c27 ("nfc: pn533: add UART phy driver")
Cc: stable@vger.kernel.org
Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
Link: https://patch.msgid.link/20260405094003.3-pn533-v2-pengpeng@iscas.ac.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Pengpeng Hou
2026-04-05 08:40:00 +08:00
committed by Paolo Abeni
parent ebe560ea5f
commit c71ba669b5
1 changed files with 8 additions and 3 deletions
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11
drivers/nfc/pn533/uart.c
View File

@@ -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;