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    Subject[11/21] eCryptfs: Infinite loop due to overflow in ecryptfs_write()
    2.6.32-longterm review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Li Wang <liwang@nudt.edu.cn>

    commit 684a3ff7e69acc7c678d1a1394fe9e757993fd34 upstream.

    ecryptfs_write() can enter an infinite loop when truncating a file to a
    size larger than 4G. This only happens on architectures where size_t is
    represented by 32 bits.

    This was caused by a size_t overflow due to it incorrectly being used to
    store the result of a calculation which uses potentially large values of
    type loff_t.

    [tyhicks@canonical.com: rewrite subject and commit message]
    Signed-off-by: Li Wang <liwang@nudt.edu.cn>
    Signed-off-by: Yunchuan Wen <wenyunchuan@kylinos.com.cn>
    Reviewed-by: Cong Wang <xiyou.wangcong@gmail.com>
    Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ecryptfs/read_write.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/fs/ecryptfs/read_write.c
    +++ b/fs/ecryptfs/read_write.c
    @@ -134,7 +134,7 @@ int ecryptfs_write(struct file *ecryptfs
    pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
    size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
    size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
    - size_t total_remaining_bytes = ((offset + size) - pos);
    + loff_t total_remaining_bytes = ((offset + size) - pos);

    if (fatal_signal_pending(current)) {
    rc = -EINTR;
    @@ -145,7 +145,7 @@ int ecryptfs_write(struct file *ecryptfs
    num_bytes = total_remaining_bytes;
    if (pos < offset) {
    /* remaining zeros to write, up to destination offset */
    - size_t total_remaining_zeros = (offset - pos);
    + loff_t total_remaining_zeros = (offset - pos);

    if (num_bytes > total_remaining_zeros)
    num_bytes = total_remaining_zeros;



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