linux-kernel - [PATCH net] NFC: hci: fix sleep in atomic context bugs in nfc_hci_hcp_message

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Message-Id: <20220516021028.54063-1-duoming@zju.edu.cn>
Date:   Mon, 16 May 2022 10:10:28 +0800
From:   Duoming Zhou <duoming@....edu.cn>
To:     linux-kernel@...r.kernel.org, krzysztof.kozlowski@...aro.org
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, gregkh@...uxfoundation.org,
        alexander.deucher@....com, broonie@...nel.org,
        netdev@...r.kernel.org, Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH net] NFC: hci: fix sleep in atomic context bugs in nfc_hci_hcp_message_tx

There are sleep in atomic context bugs when the request to secure
element of st21nfca is timeout. The root cause is that kzalloc and
alloc_skb with GFP_KERNEL parameter is called in st21nfca_se_wt_timeout
which is a timer handler. The call tree shows the execution paths that
could lead to bugs:

   (Interrupt context)
st21nfca_se_wt_timeout
  nfc_hci_send_event
    nfc_hci_hcp_message_tx
      kzalloc(..., GFP_KERNEL) //may sleep
      alloc_skb(..., GFP_KERNEL) //may sleep

This patch changes allocation mode of kzalloc and alloc_skb from
GFP_KERNEL to GFP_ATOMIC in order to prevent atomic context from
sleeping. The GFP_ATOMIC flag makes memory allocation operation
could be used in atomic context.

Fixes: 8b8d2e08bf0d ("NFC: HCI support")
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
 net/nfc/hci/hcp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/nfc/hci/hcp.c b/net/nfc/hci/hcp.c
index 05c60988f59..1caf9c2086f 100644
--- a/net/nfc/hci/hcp.c
+++ b/net/nfc/hci/hcp.c
@@ -30,7 +30,7 @@ int nfc_hci_hcp_message_tx(struct nfc_hci_dev *hdev, u8 pipe,
 	int hci_len, err;
 	bool firstfrag = true;
 
-	cmd = kzalloc(sizeof(struct hci_msg), GFP_KERNEL);
+	cmd = kzalloc(sizeof(*cmd), GFP_ATOMIC);
 	if (cmd == NULL)
 		return -ENOMEM;
 
@@ -58,7 +58,7 @@ int nfc_hci_hcp_message_tx(struct nfc_hci_dev *hdev, u8 pipe,
 			  data_link_len + ndev->tx_tailroom;
 		hci_len -= data_link_len;
 
-		skb = alloc_skb(skb_len, GFP_KERNEL);
+		skb = alloc_skb(skb_len, GFP_ATOMIC);
 		if (skb == NULL) {
 			err = -ENOMEM;
 			goto out_skb_err;
-- 
2.17.1