• Yonatan Cohen's avatar
    IB/umad: Fix kernel crash while unloading ib_umad · 9ea04d0d
    Yonatan Cohen authored
    When disassociating a device from umad we must ensure that the sysfs
    access is prevented before blocking the fops, otherwise assumptions in
    syfs don't hold:
    
    	    CPU0            	        CPU1
    	 ib_umad_kill_port()        ibdev_show()
    	    port->ib_dev = NULL
                                          dev_name(port->ib_dev)
    
    The prior patch made an error in moving the device_destroy(), it should
    have been split into device_del() (above) and put_device() (below). At
    this point we already have the split, so move the device_del() back to its
    original place.
    
      kernel stack
      PF: error_code(0x0000) - not-present page
      Oops: 0000 [#1] SMP DEBUG_PAGEALLOC PTI
      RIP: 0010:ibdev_show+0x18/0x50 [ib_umad]
      RSP: 0018:ffffc9000097fe40 EFLAGS: 00010282
      RAX: 0000000000000000 RBX: ffffffffa0441120 RCX: ffff8881df514000
      RDX: ffff8881df514000 RSI: ffffffffa0441120 RDI: ffff8881df1e8870
      RBP: ffffffff81caf000 R08: ffff8881df1e8870 R09: 0000000000000000
      R10: 0000000000001000 R11: 0000000000000003 R12: ffff88822f550b40
      R13: 0000000000000001 R14: ffffc9000097ff08 R15: ffff8882238bad58
      FS:  00007f1437ff3740(0000) GS:ffff888236940000(0000) knlGS:0000000000000000
      CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      CR2: 00000000000004e8 CR3: 00000001e0dfc001 CR4: 00000000001606e0
      Call Trace:
       dev_attr_show+0x15/0x50
       sysfs_kf_seq_show+0xb8/0x1a0
       seq_read+0x12d/0x350
       vfs_read+0x89/0x140
       ksys_read+0x55/0xd0
       do_syscall_64+0x55/0x1b0
       entry_SYSCALL_64_after_hwframe+0x44/0xa9:
    
    Fixes: cf7ad303 ("IB/umad: Avoid destroying device while it is accessed")
    Link: https://lore.kernel.org/r/20200212072635.682689-9-leon@kernel.orgSigned-off-by: default avatarYonatan Cohen <yonatanc@mellanox.com>
    Signed-off-by: default avatarLeon Romanovsky <leonro@mellanox.com>
    Reviewed-by: default avatarJason Gunthorpe <jgg@mellanox.com>
    Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
    9ea04d0d
user_mad.c 35.5 KB