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authorLin Ma <linma@zju.edu.cn>2022-05-18 18:53:21 +0800
committerDavid S. Miller <davem@davemloft.net>2022-05-18 13:58:13 +0100
commitb8cedb7093b2d1394cae9b86494cba4b62d3a30a (patch)
tree1c59ad41974251fe8d257fda44ed834264fb6fa3 /drivers
parent575fb4fb02b391ed60e5b041acda136f78e7779c (diff)
nfc: pn533: Fix buggy cleanup order
When removing the pn533 device (i2c or USB), there is a logic error. The original code first cancels the worker (flush_delayed_work) and then destroys the workqueue (destroy_workqueue), leaving the timer the last one to be deleted (del_timer). This result in a possible race condition in a multi-core preempt-able kernel. That is, if the cleanup (pn53x_common_clean) is concurrently run with the timer handler (pn533_listen_mode_timer), the timer can queue the poll_work to the already destroyed workqueue, causing use-after-free. This patch reorder the cleanup: it uses the del_timer_sync to make sure the handler is finished before the routine will destroy the workqueue. Note that the timer cannot be activated by the worker again. static void pn533_wq_poll(struct work_struct *work) ... rc = pn533_send_poll_frame(dev); if (rc) return; if (cur_mod->len == 0 && dev->poll_mod_count > 1) mod_timer(&dev->listen_timer, ...); That is, the mod_timer can be called only when pn533_send_poll_frame() returns no error, which is impossible because the device is detaching and the lower driver should return ENODEV code. Signed-off-by: Lin Ma <linma@zju.edu.cn> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/nfc/pn533/pn533.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/nfc/pn533/pn533.c b/drivers/nfc/pn533/pn533.c
index a491db46e3bd..d9f6367b9993 100644
--- a/drivers/nfc/pn533/pn533.c
+++ b/drivers/nfc/pn533/pn533.c
@@ -2787,13 +2787,14 @@ void pn53x_common_clean(struct pn533 *priv)
{
struct pn533_cmd *cmd, *n;
+ /* delete the timer before cleanup the worker */
+ del_timer_sync(&priv->listen_timer);
+
flush_delayed_work(&priv->poll_work);
destroy_workqueue(priv->wq);
skb_queue_purge(&priv->resp_q);
- del_timer(&priv->listen_timer);
-
list_for_each_entry_safe(cmd, n, &priv->cmd_queue, queue) {
list_del(&cmd->queue);
kfree(cmd);