linux-kernel - [PATCH] NFC: nxp-nci: fix deadlock during firmware update

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Date:   Tue, 12 Jul 2022 17:25:54 +0200
From:   Michael Walle <michael@...le.cc>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>,
        Michael Walle <michael@...le.cc>
Subject: [PATCH] NFC: nxp-nci: fix deadlock during firmware update

During firmware update, both nxp_nci_i2c_irq_thread_fn() and
nxp_nci_fw_work() will hold the info_lock mutex and one will wait
for the other via a completion:

nxp_nci_fw_work()
  mutex_lock(info_lock)
  nxp_nci_fw_send()
    wait_for_completion(cmd_completion)
  mutex_unlock(info_lock)

nxp_nci_i2c_irq_thread_fn()
  mutex_lock(info_lock)
    nxp_nci_fw_recv_frame()
      complete(cmd_completion)
  mutex_unlock(info_lock)

This will result in a -ETIMEDOUT error during firmware update (note
that the wait_for_completion() above is a variant with a timeout).

Drop the lock in nxp_nci_fw_work() and instead take it after the
work is done in nxp_nci_fw_work_complete() when the NFC controller mode
is switched and the info structure is updated.

Fixes: dece45855a8b ("NFC: nxp-nci: Add support for NXP NCI chips")
Signed-off-by: Michael Walle <michael@...le.cc>
---
 drivers/nfc/nxp-nci/firmware.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/nfc/nxp-nci/firmware.c b/drivers/nfc/nxp-nci/firmware.c
index 119bf305c642..6a4d4aa7239f 100644
--- a/drivers/nfc/nxp-nci/firmware.c
+++ b/drivers/nfc/nxp-nci/firmware.c
@@ -54,6 +54,7 @@ void nxp_nci_fw_work_complete(struct nxp_nci_info *info, int result)
 	struct nxp_nci_fw_info *fw_info = &info->fw_info;
 	int r;
 
+	mutex_lock(&info->info_lock);
 	if (info->phy_ops->set_mode) {
 		r = info->phy_ops->set_mode(info->phy_id, NXP_NCI_MODE_COLD);
 		if (r < 0 && result == 0)
@@ -66,6 +67,7 @@ void nxp_nci_fw_work_complete(struct nxp_nci_info *info, int result)
 		release_firmware(fw_info->fw);
 		fw_info->fw = NULL;
 	}
+	mutex_unlock(&info->info_lock);
 
 	nfc_fw_download_done(info->ndev->nfc_dev, fw_info->name, (u32) -result);
 }
@@ -172,8 +174,6 @@ void nxp_nci_fw_work(struct work_struct *work)
 	fw_info = container_of(work, struct nxp_nci_fw_info, work);
 	info = container_of(fw_info, struct nxp_nci_info, fw_info);
 
-	mutex_lock(&info->info_lock);
-
 	r = fw_info->cmd_result;
 	if (r < 0)
 		goto exit_work;
@@ -190,7 +190,6 @@ void nxp_nci_fw_work(struct work_struct *work)
 exit_work:
 	if (r < 0 || fw_info->size == 0)
 		nxp_nci_fw_work_complete(info, r);
-	mutex_unlock(&info->info_lock);
 }
 
 int nxp_nci_fw_download(struct nci_dev *ndev, const char *firmware_name)
-- 
2.30.2