[PATCH 04/22] fsnotify: Remove fsnotify_duplicate_mark()

[Paul Moore]

On Fri, Dec 23, 2016 at 8:22 AM, Jan Kara <jack at suse.cz> wrote:
> On Thu 22-12-16 18:13:11, Paul Moore wrote:
>> On Thu, Dec 22, 2016 at 4:15 AM, Jan Kara <jack at suse.cz> wrote:
>> > There are only two calls sites of fsnotify_duplicate_mark(). Those are
>> > in kernel/audit_tree.c and both are bogus. Vfsmount pointer is unused
>> > for audit tree, inode pointer and group gets set in
>> > fsnotify_add_mark_locked() later anyway, mask and free_mark are already
>> > set in alloc_chunk(). In fact, calling fsnotify_duplicate_mark() is
>> > actively harmful because following fsnotify_add_mark_locked() will leak
>> > group reference by overwriting the group pointer. So just remove the two
>> > calls to fsnotify_duplicate_mark() and the function.
>> >
>> > Signed-off-by: Jan Kara <jack at suse.cz>
>> > ---
>> >  fs/notify/mark.c                 | 12 ------------
>> >  include/linux/fsnotify_backend.h |  2 --
>> >  kernel/audit_tree.c              |  6 ++----
>> >  3 files changed, 2 insertions(+), 18 deletions(-)
>>
>> At first glance this looks reasonable, although you keep mentioning
>> "fsnotify_add_mark_locked" above when untag_chunk() is calling
>> "fsnotify_add_mark"; I just wanted to make sure you hadn't intended to
>> take the mutex in the audit code instead of relying on the locking in
>> fsnotify_add_mark().
>
> No, I didn't want to take mutex in the audit code. It is just that
> fsnotify_add_mark() is a thin wrapper around fsnotify_add_mark_locked() so
> I was speaking about that function.

Understood.  I just wanted to make sure this is what you intended
since the commit description and patch did not match.

If you end up respinning the patchset for any reason I might suggest
changing the function name in the description above.

>>
>> > diff --git a/fs/notify/mark.c b/fs/notify/mark.c
>> > index d3fea0bd89e2..6043306e8e21 100644
>> > --- a/fs/notify/mark.c
>> > +++ b/fs/notify/mark.c
>> > @@ -510,18 +510,6 @@ void fsnotify_detach_group_marks(struct fsnotify_group *group)
>> >         }
>> >  }
>> >
>> > -void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old)
>> > -{
>> > -       assert_spin_locked(&old->lock);
>> > -       new->inode = old->inode;
>> > -       new->mnt = old->mnt;
>> > -       if (old->group)
>> > -               fsnotify_get_group(old->group);
>> > -       new->group = old->group;
>> > -       new->mask = old->mask;
>> > -       new->free_mark = old->free_mark;
>> > -}
>> > -
>> >  /*
>> >   * Nothing fancy, just initialize lists and locks and counters.
>> >   */
>> > diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
>> > index 0cf34d6cc253..487246546ebe 100644
>> > --- a/include/linux/fsnotify_backend.h
>> > +++ b/include/linux/fsnotify_backend.h
>> > @@ -323,8 +323,6 @@ extern void fsnotify_init_mark(struct fsnotify_mark *mark, void (*free_mark)(str
>> >  extern struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group, struct inode *inode);
>> >  /* find (and take a reference) to a mark associated with group and vfsmount */
>> >  extern struct fsnotify_mark *fsnotify_find_vfsmount_mark(struct fsnotify_group *group, struct vfsmount *mnt);
>> > -/* copy the values from old into new */
>> > -extern void fsnotify_duplicate_mark(struct fsnotify_mark *new, struct fsnotify_mark *old);
>> >  /* set the ignored_mask of a mark */
>> >  extern void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mask);
>> >  /* set the mask of a mark (might pin the object into memory */
>> > diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
>> > index 8b1dde96a0fa..f3130eb0a4bd 100644
>> > --- a/kernel/audit_tree.c
>> > +++ b/kernel/audit_tree.c
>> > @@ -258,8 +258,7 @@ static void untag_chunk(struct node *p)
>> >         if (!new)
>> >                 goto Fallback;
>> >
>> > -       fsnotify_duplicate_mark(&new->mark, entry);
>> > -       if (fsnotify_add_mark(&new->mark, new->mark.group, new->mark.inode, NULL, 1)) {
>> > +       if (fsnotify_add_mark(&new->mark, entry->group, entry->inode, NULL, 1)) {
>> >                 fsnotify_put_mark(&new->mark);
>> >                 goto Fallback;
>> >         }
>> > @@ -395,8 +394,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
>> >                 return -ENOENT;
>> >         }
>> >
>> > -       fsnotify_duplicate_mark(chunk_entry, old_entry);
>> > -       if (fsnotify_add_mark(chunk_entry, chunk_entry->group, chunk_entry->inode, NULL, 1)) {
>> > +       if (fsnotify_add_mark(chunk_entry, old_entry->group, old_entry->inode, NULL, 1)) {
>> >                 spin_unlock(&old_entry->lock);
>> >                 fsnotify_put_mark(chunk_entry);
>> >                 fsnotify_put_mark(old_entry);
>> > --
>> > 2.10.2
>> >
>>
>> --
>> paul moore
>> www.paul-moore.com
> --
> Jan Kara <jack at suse.com>
> SUSE Labs, CR



-- 
paul moore
www.paul-moore.com