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Subject[PATCH net] NFC: hci: fix sleep in atomic context bugs in nfc_hci_hcp_message_tx
Date
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@zju.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
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