tree 43bb2d70b4d933183fcf56ab1eb9ac8e3d83f1ab
parent 671762f8071563847e50f45c6fb0b329e6e8cf9a
author Yan, Zheng <zyan@redhat.com> 1420529354 +0800
committer Ilya Dryomov <idryomov@gmail.com> 1424341898 +0300

ceph: properly zero data pages for file holes.

A bug is found in striped_read() of fs/ceph/file.c. striped_read() calls
ceph_zero_pape_vector_range().  The first argument, page_align + read + ret,
passed to ceph_zero_pape_vector_range() is wrong.

When a file has holes, this wrong parameter may cause memory corruption
either in kernal space or user space. Kernel space memory may be corrupted in
the case of non direct IO; user space memory may be corrupted in the case of
direct IO. In the latter case, the application doing direct IO may crash due
to memory corruption, as we have experienced.

The correct value should be initial_align + read + ret, where intial_align =
o_direct ? buf_align : io_align.  Compared with page_align, the current page
offest, initial_align is the initial page offest, which should be used to
calculate the page and offset in ceph_zero_pape_vector_range().

Reported-by: caifeng zhu <zhucaifeng@unissoft-nj.com>
Signed-off-by: Yan, Zheng <zyan@redhat.com>