tree 46892bcb975cce092aea2f476fcfc5153f7cd3e5
parent 18a18172c829b5ca044691998ed21bcafe3773a5
author Lin Ma <linma@zju.edu.cn> 1636988160 +0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1637923722 +0100

NFC: reorganize the functions in nci_request

[ Upstream commit 86cdf8e38792545161dbe3350a7eced558ba4d15 ]

There is a possible data race as shown below:

thread-A in nci_request()       | thread-B in nci_close_device()
                                | mutex_lock(&ndev->req_lock);
test_bit(NCI_UP, &ndev->flags); |
...                             | test_and_clear_bit(NCI_UP, &ndev->flags)
mutex_lock(&ndev->req_lock);    |
                                |

This race will allow __nci_request() to be awaked while the device is
getting removed.

Similar to commit e2cb6b891ad2 ("bluetooth: eliminate the potential race
condition when removing the HCI controller"). this patch alters the
function sequence in nci_request() to prevent the data races between the
nci_close_device().

Signed-off-by: Lin Ma <linma@zju.edu.cn>
Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation")
Link: https://lore.kernel.org/r/20211115145600.8320-1-linma@zju.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>