• Z
    filp->f_pos not correctly updated in proc_task_readdir · ee6f779b
    Zhang Le 提交于
    filp->f_pos only get updated at the end of the function. Thus d_off of those
    dirents who are in the middle will be 0, and this will cause a problem in
    glibc's readdir implementation, specifically endless loop. Because when overflow
    occurs, f_pos will be set to next dirent to read, however it will be 0, unless
    the next one is the last one. So it will start over again and again.
    
    There is a sample program in man 2 gendents. This is the output of the program
    running on a multithread program's task dir before this patch is applied:
    
      $ ./a.out /proc/3807/task
      --------------- nread=128 ---------------
      i-node#  file type  d_reclen  d_off   d_name
        506442  directory    16          1  .
        506441  directory    16          0  ..
        506443  directory    16          0  3807
        506444  directory    16          0  3809
        506445  directory    16          0  3812
        506446  directory    16          0  3861
        506447  directory    16          0  3862
        506448  directory    16          8  3863
    
    This is the output after this patch is applied
    
      $ ./a.out /proc/3807/task
      --------------- nread=128 ---------------
      i-node#  file type  d_reclen  d_off   d_name
        506442  directory    16          1  .
        506441  directory    16          2  ..
        506443  directory    16          3  3807
        506444  directory    16          4  3809
        506445  directory    16          5  3812
        506446  directory    16          6  3861
        506447  directory    16          7  3862
        506448  directory    16          8  3863
    Signed-off-by: NZhang Le <r0bertz@gentoo.org>
    Acked-by: NAl Viro <viro@ZenIV.linux.org.uk>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    ee6f779b
base.c 74.4 KB