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    SubjectRe: [PATCH 6/6] vfs: introduce FMODE_NEG_OFFSET for allowing negative f_pos
    On Sat, 16 Jan 2010 21:54:39 +0900
    OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> wrote:

    > Wu Fengguang <fengguang.wu@intel.com> writes:
    >
    > > +static int
    > > +__negative_fpos_check(struct file *file, loff_t pos, size_t count)
    > > +{
    > > + /*
    > > + * pos or pos+count is negative here, check overflow.
    > > + * too big "count" will be caught in rw_verify_area().
    > > + */
    > > + if ((pos < 0) && (pos + count < pos))
    > > + return -EOVERFLOW;
    > > + if (file->f_mode & FMODE_NEG_OFFSET)
    > > + return 0;
    > > + return -EINVAL;
    > > +}
    > > +
    > > /*
    > > * rw_verify_area doesn't like huge counts. We limit
    > > * them to something that fits in "int" so that others
    > > @@ -222,8 +236,11 @@ int rw_verify_area(int read_write, struc
    > > if (unlikely((ssize_t) count < 0))
    > > return retval;
    > > pos = *ppos;
    > > - if (unlikely((pos < 0) || (loff_t) (pos + count) < 0))
    > > - return retval;
    > > + if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) {
    > > + retval = __negative_fpos_check(file, pos, count);
    > > + if (retval)
    > > + return retval;
    > > + }
    > >
    > > if (unlikely(inode->i_flock && mandatory_lock(inode))) {
    > > retval = locks_mandatory_area(
    >
    > Um... How do lseek() work? It sounds like to violate error code range.

    This is for read-write. As far as I know,
    - generic_file_llseek,
    - default_llseek
    - no_llseek

    doesn't call this function.

    Thanks,
    -Kame



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