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SubjectRe: [PATCH] CDRW packet writing support for 2.6.7-bk13
On Fri, Jul 02, 2004 at 03:08:19PM -0700, Andrew Morton wrote:
> Peter Osterlund <petero2@telia.com> wrote:
> >
> > This code leaks a module reference. The patch below fixes it. I'm not
> > sure it's correct, but do_open() also does module_put() after
> > put_disk().
> >
> > Signed-off-by: Peter Osterlund <petero2@telia.com>
> >
> > ---
> >
> > linux-petero/fs/partitions/check.c | 1 +
> > 1 files changed, 1 insertion(+)
> >
> > diff -puN fs/partitions/check.c~packet-refcnt fs/partitions/check.c
> > --- linux/fs/partitions/check.c~packet-refcnt 2004-07-02 23:18:22.000000000 +0200
> > +++ linux-petero/fs/partitions/check.c 2004-07-02 23:18:23.000000000 +0200
> > @@ -151,6 +151,7 @@ const char *__bdevname(dev_t dev, char *
> > if (disk) {
> > buffer = disk_name(disk, part, buffer);
> > put_disk(disk);
> > + module_put(disk->fops->owner);
> > } else {
> > snprintf(buffer, BDEVNAME_SIZE, "unknown-block(%u,%u)",
> > MAJOR(dev), MINOR(dev));
>
> Yes, there's certainly a leak there. It's surprising that it hasn't been
> noted before.
>
> But:
>
> const char *__bdevname(dev_t dev, char *buffer)
> {
> struct gendisk *disk;
> int part;
>
> disk = get_gendisk(dev, &part);
> if (disk) {
> buffer = disk_name(disk, part, buffer);
> put_disk(disk);
> } else {
> snprintf(buffer, BDEVNAME_SIZE, "unknown-block(%u,%u)",
> MAJOR(dev), MINOR(dev));
> }
>
> get_gendisk() did an internal module_get() in kobj_lookup().

But if kobj_lookup() succeeds, module_put() is called before returning
(actually it's always called, right?)

> It would seem to be logical that the module_put() should be in
> kobject_put(), called from put_disk(). But surely if we made that
> change 1000 things would explode.

I don't see how that would fix anything, as the module reference is not
held after kobj_lookup() returns. Or am I missing something here?

thanks,

greg k-h
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