writeback: avoid use-after-free after removing device
commit f87904c075515f3e1d8f4a7115869d3b914674fd upstream.
When a disk is removed, bdi_unregister gets called to stop further
writeback and wait for associated delayed work to complete. However,
wb_inode_writeback_end() may schedule bandwidth estimation dwork after
this has completed, which can result in the timer attempting to access the
just freed bdi_writeback.
Fix this by checking if the bdi_writeback is alive, similar to when
scheduling writeback work.
Since this requires wb->work_lock, and wb_inode_writeback_end() may get
called from interrupt, switch wb->work_lock to an irqsafe lock.
Link: https://lkml.kernel.org/r/20220801155034.3772543-1-khazhy@google.com
Fixes: 45a2966fd641 ("writeback: fix bandwidth estimate for spiky workload")
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Michael Stapelberg <stapelberg+linux@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 02c9d5c..142e118 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -258,10 +258,10 @@ void wb_wakeup_delayed(struct bdi_writeback *wb)
unsigned long timeout;
timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
- spin_lock_bh(&wb->work_lock);
+ spin_lock_irq(&wb->work_lock);
if (test_bit(WB_registered, &wb->state))
queue_delayed_work(bdi_wq, &wb->dwork, timeout);
- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);
}
static void wb_update_bandwidth_workfn(struct work_struct *work)
@@ -337,12 +337,12 @@ static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
static void wb_shutdown(struct bdi_writeback *wb)
{
/* Make sure nobody queues further work */
- spin_lock_bh(&wb->work_lock);
+ spin_lock_irq(&wb->work_lock);
if (!test_and_clear_bit(WB_registered, &wb->state)) {
- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);
return;
}
- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);
cgwb_remove_from_bdi_list(wb);
/*