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    Subject[PATCH 4.4 063/108] kernfs: fix regression in kernfs_fop_write caused by wrong type
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Ivan Vecera <ivecera@redhat.com>

    commit ba87977a49913129962af8ac35b0e13e0fa4382d upstream.

    Commit b7ce40cff0b9 ("kernfs: cache atomic_write_len in
    kernfs_open_file") changes type of local variable 'len' from ssize_t
    to size_t. This change caused that the *ppos value is updated also
    when the previous write callback failed.

    Mentioned snippet:
    ...
    len = ops->write(...); <- return value can be negative
    ...
    if (len > 0) <- true here in this case
    *ppos += len;
    ...

    Fixes: b7ce40cff0b9 ("kernfs: cache atomic_write_len in kernfs_open_file")
    Acked-by: Tejun Heo <tj@kernel.org>
    Signed-off-by: Ivan Vecera <ivecera@redhat.com>
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/kernfs/file.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/fs/kernfs/file.c
    +++ b/fs/kernfs/file.c
    @@ -272,7 +272,7 @@ static ssize_t kernfs_fop_write(struct f
    {
    struct kernfs_open_file *of = kernfs_of(file);
    const struct kernfs_ops *ops;
    - size_t len;
    + ssize_t len;
    char *buf;

    if (of->atomic_write_len) {

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