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Subject[PATCH] drivers: nfc: nfcmrvl: fix double free bug in nfcmrvl_nci_unregister_dev()
Date
There is a potential double bug in nfcmrvl usb driver between
unregister and resume operation.

The race that cause that double free bug can be shown as below:

(FREE) | (USE)
| nfcmrvl_resume
| nfcmrvl_submit_bulk_urb
| nfcmrvl_bulk_complete
| nfcmrvl_nci_recv_frame
| nfcmrvl_fw_dnld_recv_frame
| queue_work
| fw_dnld_rx_work
| fw_dnld_over
| release_firmware
| kfree(fw); //(1)
nfcmrvl_disconnect |
nfcmrvl_nci_unregister_dev |
nfcmrvl_fw_dnld_abort |
fw_dnld_over | ...
if (priv->fw_dnld.fw) |
release_firmware |
kfree(fw); //(2) |
... | fw = NULL;

When nfcmrvl usb driver is resuming, we detach the device.
The release_firmware() will deallocate firmware in position (1),
but firmware will be deallocated again in position (2), which
leads to double free.

This patch reorders nfcmrvl_fw_dnld_deinit() before nfcmrvl_fw_dnld_abort()
in order to prevent double free bug. Because destroy_workqueue() will
not return until all work is finished.

Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
---
drivers/nfc/nfcmrvl/main.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/nfc/nfcmrvl/main.c b/drivers/nfc/nfcmrvl/main.c
index 2fcf545012b..d8342271f50 100644
--- a/drivers/nfc/nfcmrvl/main.c
+++ b/drivers/nfc/nfcmrvl/main.c
@@ -183,11 +183,10 @@ void nfcmrvl_nci_unregister_dev(struct nfcmrvl_private *priv)
{
struct nci_dev *ndev = priv->ndev;

+ nfcmrvl_fw_dnld_deinit(priv);
if (priv->ndev->nfc_dev->fw_download_in_progress)
nfcmrvl_fw_dnld_abort(priv);

- nfcmrvl_fw_dnld_deinit(priv);
-
if (gpio_is_valid(priv->config.reset_n_io))
gpio_free(priv->config.reset_n_io);

--
2.17.1
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