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    vfs: iov_iter: have iov_iter_advance decrement nr_segs appropriately · 39be79c1
    Jeff Layton 提交于
    Currently, when you call iov_iter_advance, then the pointer to the iovec
    array can be incremented, but it does not decrement the nr_segs value in
    the iov_iter struct. The result is a iov_iter struct with a nr_segs
    value that goes beyond the end of the array.
    
    While I'm not aware of anything that's specifically broken by this, it
    seems odd and a bit dangerous not to decrement that value. If someone
    were to trust the nr_segs value to be correct, then they could end up
    walking off the end of the array.
    
    Changing this might also provide some micro-optimization when dealing
    with the last iovec in an array. Many of the other routines that deal
    with iov_iter have optimized codepaths when nr_segs == 1.
    
    Cc: Nick Piggin <npiggin@suse.de>
    Signed-off-by: NJeff Layton <jlayton@redhat.com>
    Signed-off-by: NChristoph Hellwig <hch@lst.de>
    39be79c1
filemap.c 69.9 KB