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    Subject[v2.6.34-stable 096/165] um: fix ubd cow size
    Date
    From: Richard Weinberger <richard@nod.at>

    -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
    -------------------

    commit 8535639810e578960233ad39def3ac2157b0c3ec upstream.

    ubd_file_size() cannot use ubd_dev->cow.file because at this time
    ubd_dev->cow.file is not initialized.
    Therefore, ubd_file_size() will always report a wrong disk size when
    COW files are used.
    Reading from /dev/ubd* would crash the kernel.

    We have to read the correct disk size from the COW file's backing
    file.

    Signed-off-by: Richard Weinberger <richard@nod.at>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    arch/um/drivers/ubd_kern.c | 31 ++++++++++++++++++++++++++++++-
    1 file changed, 30 insertions(+), 1 deletion(-)

    diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
    index 3d63b83..1cbad01 100644
    --- a/arch/um/drivers/ubd_kern.c
    +++ b/arch/um/drivers/ubd_kern.c
    @@ -511,8 +511,37 @@ __uml_exitcall(kill_io_thread);
    static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
    {
    char *file;
    + int fd;
    + int err;
    +
    + __u32 version;
    + __u32 align;
    + char *backing_file;
    + time_t mtime;
    + unsigned long long size;
    + int sector_size;
    + int bitmap_offset;
    +
    + if (ubd_dev->file && ubd_dev->cow.file) {
    + file = ubd_dev->cow.file;
    +
    + goto out;
    + }

    - file = ubd_dev->cow.file ? ubd_dev->cow.file : ubd_dev->file;
    + fd = os_open_file(ubd_dev->file, global_openflags, 0);
    + if (fd < 0)
    + return fd;
    +
    + err = read_cow_header(file_reader, &fd, &version, &backing_file, \
    + &mtime, &size, &sector_size, &align, &bitmap_offset);
    + os_close_file(fd);
    +
    + if(err == -EINVAL)
    + file = ubd_dev->file;
    + else
    + file = backing_file;
    +
    +out:
    return os_file_size(file, size_out);
    }

    --
    1.7.12.rc2


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