• Mikulas Patocka's avatar
    dm: avoid _hash_lock deadlock · 6076905b
    Mikulas Patocka authored
    Fix a reported deadlock if there are still unprocessed multipath events
    on a device that is being removed.
    
    _hash_lock is held during dev_remove while trying to send the
    outstanding events.  Sending the events requests the _hash_lock
    again in dm_copy_name_and_uuid.
    
    This patch introduces a separate lock around regions that modify the
    link to the hash table (dm_set_mdptr) or the name or uuid so that
    dm_copy_name_and_uuid no longer needs _hash_lock.
    
    Additionally, dm_copy_name_and_uuid can only be called if md exists
    so we can drop the dm_get() and dm_put() which can lead to a BUG()
    while md is being freed.
    
    The deadlock:
     #0 [ffff8106298dfb48] schedule at ffffffff80063035
     #1 [ffff8106298dfc20] __down_read at ffffffff8006475d
     #2 [ffff8106298dfc60] dm_copy_name_and_uuid at ffffffff8824f740
     #3 [ffff8106298dfc90] dm_send_uevents at ffffffff88252685
     #4 [ffff8106298dfcd0] event_callback at ffffffff8824c678
     #5 [ffff8106298dfd00] dm_table_event at ffffffff8824dd01
     #6 [ffff8106298dfd10] __hash_remove at ffffffff882507ad
     #7 [ffff8106298dfd30] dev_remove at ffffffff88250865
     #8 [ffff8106298dfd60] ctl_ioctl at ffffffff88250d80
     #9 [ffff8106298dfee0] do_ioctl at ffffffff800418c4
    #10 [ffff8106298dff00] vfs_ioctl at ffffffff8002fab9
    #11 [ffff8106298dff40] sys_ioctl at ffffffff8004bdaf
    #12 [ffff8106298dff80] tracesys at ffffffff8005d28d (via system_call)
    
    Cc: stable@kernel.org
    Reported-by: default avatarguy keren <choo@actcom.co.il>
    Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
    Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
    6076905b
dm-uevent.c 5.31 KB