• Zhiqiang Liu's avatar
    brd: check and limit max_part par · c8ab4225
    Zhiqiang Liu authored
    In brd_init func, rd_nr num of brd_device are firstly allocated
    and add in brd_devices, then brd_devices are traversed to add each
    brd_device by calling add_disk func. When allocating brd_device,
    the disk->first_minor is set to i * max_part, if rd_nr * max_part
    is larger than MINORMASK, two different brd_device may have the same
    devt, then only one of them can be successfully added.
    when rmmod brd.ko, it will cause oops when calling brd_exit.
    
    Follow those steps:
      # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576
      # rmmod brd
    then, the oops will appear.
    
    Oops log:
    [  726.613722] Call trace:
    [  726.614175]  kernfs_find_ns+0x24/0x130
    [  726.614852]  kernfs_find_and_get_ns+0x44/0x68
    [  726.615749]  sysfs_remove_group+0x38/0xb0
    [  726.616520]  blk_trace_remove_sysfs+0x1c/0x28
    [  726.617320]  blk_unregister_queue+0x98/0x100
    [  726.618105]  del_gendisk+0x144/0x2b8
    [  726.618759]  brd_exit+0x68/0x560 [brd]
    [  726.619501]  __arm64_sys_delete_module+0x19c/0x2a0
    [  726.620384]  el0_svc_common+0x78/0x130
    [  726.621057]  el0_svc_handler+0x38/0x78
    [  726.621738]  el0_svc+0x8/0xc
    [  726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)
    
    Here, we add brd_check_and_reset_par func to check and limit max_part par.
    
    --
    V5->V6:
     - remove useless code
    
    V4->V5:(suggested by Ming Lei)
     - make sure max_part is not larger than DISK_MAX_PARTS
    
    V3->V4:(suggested by Ming Lei)
     - remove useless change
     - add one limit of max_part
    
    V2->V3: (suggested by Ming Lei)
     - clear .minors when running out of consecutive minor space in brd_alloc
     - remove limit of rd_nr
    
    V1->V2:
     - add more checks in brd_check_par_valid as suggested by Ming Lei.
    Signed-off-by: default avatarZhiqiang Liu <liuzhiqiang26@huawei.com>
    Reviewed-by: default avatarBob Liu <bob.liu@oracle.com>
    Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    c8ab4225
brd.c 13.3 KB