On Thu, Dec 22, 2016 at 4:15 AM, Jan Kara <jack@xxxxxxx> 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@xxxxxxx>
> ---
> 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().
> 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
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