[PATCH net v2] atm: fore200e: fix use-after-free in tasklets during device removal

When the PCA-200E or SBA-200E adapter is being detached, the fore200e
is deallocated. However, the tx_tasklet or rx_tasklet may still be running
or pending, leading to use-after-free bug when the already freed fore200e
is accessed again in fore200e_tx_tasklet() or fore200e_rx_tasklet().

One of the race conditions can occur as follows:

CPU 0 (cleanup)           | CPU 1 (tasklet)
fore200e_pca_remove_one() | fore200e_interrupt()
  fore200e_shutdown()     |   tasklet_schedule()
    kfree(fore200e)       | fore200e_tx_tasklet()
                          |   fore200e-> // UAF

Fix this by ensuring tx_tasklet or rx_tasklet is properly canceled before
the fore200e is released. Add tasklet_kill() in fore200e_shutdown() to
synchronize with any pending or running tasklets. Moreover, since
fore200e_reset() could prevent further interrupts or data transfers,
the tasklet_kill() should be placed after fore200e_reset() to prevent
the tasklet from being rescheduled in fore200e_interrupt().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Duoming Zhou <redacted>
---
Changes in v2:
  - Move tasklet_kill() after fore200e_reset().

 drivers/atm/fore200e.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/atm/fore200e.c b/drivers/atm/fore200e.c
index f62e3857144..de04c407921 100644
--- a/drivers/atm/fore200e.c
+++ b/drivers/atm/fore200e.c

@@ -362,6 +362,10 @@ fore200e_shutdown(struct fore200e* fore200e)
     if (fore200e->state > FORE200E_STATE_RESET) {
 	/* first, reset the board to prevent further interrupts or data transfers */
 	fore200e_reset(fore200e, 0);
+#ifdef FORE200E_USE_TASKLET
+	tasklet_kill(&fore200e->tx_tasklet);
+	tasklet_kill(&fore200e->rx_tasklet);
+#endif
     }
     
     /* then, release all allocated resources */

-- 
2.34.1