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writeback: avoid use-after-free after removing device

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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: 45a2966fd6 ("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>
This commit is contained in:
Khazhismel Kumykov
2022-08-01 08:50:34 -07:00
committed by Andrew Morton
parent 9dfb3b8d65
commit f87904c075
3 changed files with 16 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
mm/backing-dev.c
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@@ -260,10 +260,10 @@ 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)
@@ -334,12 +334,12 @@ 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);
/*