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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Duoming Zhou <duoming@zju.edu.cn>,
        Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 43/68] NFC: nci: fix sleep in atomic context bugs caused by nci_skb_alloc
Date:   Mon, 23 May 2022 19:05:10 +0200
Message-Id: <20220523165809.719807111@linuxfoundation.org>
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From: Duoming Zhou <duoming@zju.edu.cn>

[ Upstream commit 23dd4581350d4ffa23d58976ec46408f8f4c1e16 ]

There are sleep in atomic context bugs when the request to secure
element of st-nci is timeout. The root cause is that nci_skb_alloc
with GFP_KERNEL parameter is called in st_nci_se_wt_timeout which is
a timer handler. The call paths that could trigger bugs are shown below:

    (interrupt context 1)
st_nci_se_wt_timeout
  nci_hci_send_event
    nci_hci_send_data
      nci_skb_alloc(..., GFP_KERNEL) //may sleep

   (interrupt context 2)
st_nci_se_wt_timeout
  nci_hci_send_event
    nci_hci_send_data
      nci_send_data
        nci_queue_tx_data_frags
          nci_skb_alloc(..., GFP_KERNEL) //may sleep

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

Fixes: ed06aeefdac3 ("nfc: st-nci: Rename st21nfcb to st-nci")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220517012530.75714-1-duoming@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/nfc/nci/data.c | 2 +-
 net/nfc/nci/hci.c  | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/nfc/nci/data.c b/net/nfc/nci/data.c
index ce3382be937f..b002e18f38c8 100644
--- a/net/nfc/nci/data.c
+++ b/net/nfc/nci/data.c
@@ -118,7 +118,7 @@ static int nci_queue_tx_data_frags(struct nci_dev *ndev,
 
 		skb_frag = nci_skb_alloc(ndev,
 					 (NCI_DATA_HDR_SIZE + frag_len),
-					 GFP_KERNEL);
+					 GFP_ATOMIC);
 		if (skb_frag == NULL) {
 			rc = -ENOMEM;
 			goto free_exit;
diff --git a/net/nfc/nci/hci.c b/net/nfc/nci/hci.c
index 04e55ccb3383..4fe336ff2bfa 100644
--- a/net/nfc/nci/hci.c
+++ b/net/nfc/nci/hci.c
@@ -153,7 +153,7 @@ static int nci_hci_send_data(struct nci_dev *ndev, u8 pipe,
 
 	i = 0;
 	skb = nci_skb_alloc(ndev, conn_info->max_pkt_payload_len +
-			    NCI_DATA_HDR_SIZE, GFP_KERNEL);
+			    NCI_DATA_HDR_SIZE, GFP_ATOMIC);
 	if (!skb)
 		return -ENOMEM;
 
@@ -186,7 +186,7 @@ static int nci_hci_send_data(struct nci_dev *ndev, u8 pipe,
 		if (i < data_len) {
 			skb = nci_skb_alloc(ndev,
 					    conn_info->max_pkt_payload_len +
-					    NCI_DATA_HDR_SIZE, GFP_KERNEL);
+					    NCI_DATA_HDR_SIZE, GFP_ATOMIC);
 			if (!skb)
 				return -ENOMEM;
 
-- 
2.35.1