• Jiazi Li's avatar
    dm: fix mempool NULL pointer race when completing IO · d208b894
    Jiazi Li authored
    dm_io_dec_pending() calls end_io_acct() first and will then dec md
    in-flight pending count. But if a task is swapping DM table at same
    time this can result in a crash due to mempool->elements being NULL:
    
    task1                             task2
    do_resume
     ->do_suspend
      ->dm_wait_for_completion
                                      bio_endio
    				   ->clone_endio
    				    ->dm_io_dec_pending
    				     ->end_io_acct
    				      ->wakeup task1
     ->dm_swap_table
      ->__bind
       ->__bind_mempools
        ->bioset_exit
         ->mempool_exit
                                         ->free_io
    
    [ 67.330330] Unable to handle kernel NULL pointer dereference at
    virtual address 0000000000000000
    ......
    [ 67.330494] pstate: 80400085 (Nzcv daIf +PAN -UAO)
    [ 67.330510] pc : mempool_free+0x70/0xa0
    [ 67.330515] lr : mempool_free+0x4c/0xa0
    [ 67.330520] sp : ffffff8008013b20
    [ 67.330524] x29: ffffff8008013b20 x28: 0000000000000004
    [ 67.330530] x27: ffffffa8c2ff40a0 x26: 00000000ffff1cc8
    [ 67.330535] x25: 0000000000000000 x24: ffffffdada34c800
    [ 67.330541] x23: 0000000000000000 x22: ffffffdada34c800
    [ 67.330547] x21: 00000000ffff1cc8 x20: ffffffd9a1304d80
    [ 67.330552] x19: ffffffdada34c970 x18: 000000b312625d9c
    [ 67.330558] x17: 00000000002dcfbf x16: 00000000000006dd
    [ 67.330563] x15: 000000000093b41e x14: 0000000000000010
    [ 67.330569] x13: 0000000000007f7a x12: 0000000034155555
    [ 67.330574] x11: 0000000000000001 x10: 0000000000000001
    [ 67.330579] x9 : 0000000000000000 x8 : 0000000000000000
    [ 67.330585] x7 : 0000000000000000 x6 : ffffff80148b5c1a
    [ 67.330590] x5 : ffffff8008013ae0 x4 : 0000000000000001
    [ 67.330596] x3 : ffffff80080139c8 x2 : ffffff801083bab8
    [ 67.330601] x1 : 0000000000000000 x0 : ffffffdada34c970
    [ 67.330609] Call trace:
    [ 67.330616] mempool_free+0x70/0xa0
    [ 67.330627] bio_put+0xf8/0x110
    [ 67.330638] dec_pending+0x13c/0x230
    [ 67.330644] clone_endio+0x90/0x180
    [ 67.330649] bio_endio+0x198/0x1b8
    [ 67.330655] dec_pending+0x190/0x230
    [ 67.330660] clone_endio+0x90/0x180
    [ 67.330665] bio_endio+0x198/0x1b8
    [ 67.330673] blk_update_request+0x214/0x428
    [ 67.330683] scsi_end_request+0x2c/0x300
    [ 67.330688] scsi_io_completion+0xa0/0x710
    [ 67.330695] scsi_finish_command+0xd8/0x110
    [ 67.330700] scsi_softirq_done+0x114/0x148
    [ 67.330708] blk_done_softirq+0x74/0xd0
    [ 67.330716] __do_softirq+0x18c/0x374
    [ 67.330724] irq_exit+0xb4/0xb8
    [ 67.330732] __handle_domain_irq+0x84/0xc0
    [ 67.330737] gic_handle_irq+0x148/0x1b0
    [ 67.330744] el1_irq+0xe8/0x190
    [ 67.330753] lpm_cpuidle_enter+0x4f8/0x538
    [ 67.330759] cpuidle_enter_state+0x1fc/0x398
    [ 67.330764] cpuidle_enter+0x18/0x20
    [ 67.330772] do_idle+0x1b4/0x290
    [ 67.330778] cpu_startup_entry+0x20/0x28
    [ 67.330786] secondary_start_kernel+0x160/0x170
    
    Fix this by:
    1) Establishing pointers to 'struct dm_io' members in
    dm_io_dec_pending() so that they may be passed into end_io_acct()
    _after_ free_io() is called.
    2) Moving end_io_acct() after free_io().
    
    Cc: stable@vger.kernel.org
    Signed-off-by: default avatarJiazi Li <lijiazi@xiaomi.com>
    Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
    d208b894
dm.c 70.5 KB