net: alx: fix race condition in alx_remove

There is a race condition exist during termination. The path is
alx_stop and then alx_remove. An alx_schedule_link_check could be called
before alx_stop by interrupt handler and invoke alx_link_check later.
Alx_stop frees the napis, and alx_remove cancels any pending works.
If any of the work is scheduled before termination and invoked before
alx_remove, a null-ptr-deref occurs because both expect alx->napis[i].

This patch fix the race condition by moving cancel_work_sync functions
before alx_free_napis inside alx_stop. Because interrupt handler can call
alx_schedule_link_check again, alx_free_irq is moved before
cancel_work_sync calls too.

Signed-off-by: Zekun Shen <bruceshenzk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/atheros/alx/main.c b/drivers/net/ethernet/atheros/alx/main.c
index b9b4edb913c1317ddeca47354786f85964bab979..9b7f1af5f574708caf5475f62212c72d12fe942e 100644 (file)
--- a/drivers/net/ethernet/atheros/alx/main.c
+++ b/drivers/net/ethernet/atheros/alx/main.c
@@ -1249,8 +1249,12 @@ out_disable_adv_intr:
 
 static void __alx_stop(struct alx_priv *alx)
 {
-       alx_halt(alx);
        alx_free_irq(alx);
+
+       cancel_work_sync(&alx->link_check_wk);
+       cancel_work_sync(&alx->reset_wk);
+
+       alx_halt(alx);
        alx_free_rings(alx);
        alx_free_napis(alx);
 }
@@ -1855,9 +1859,6 @@ static void alx_remove(struct pci_dev *pdev)
        struct alx_priv *alx = pci_get_drvdata(pdev);
        struct alx_hw *hw = &alx->hw;
 
-       cancel_work_sync(&alx->link_check_wk);
-       cancel_work_sync(&alx->reset_wk);
-
        /* restore permanent mac address */
        alx_set_macaddr(hw, hw->perm_addr);