On Thu, Jan 4, 2018 at 5:40 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: > On a malformed overlay, several redirected dirs can point to the same > dir on a lower layer. This presents a similar challenge as broken > hardlinks, because different objects in the overlay can return the same > st_ino/st_dev pair from stat(2). > > For broken hardlinks, we do not provide constant st_ino on copy up to > avoid this inconsistency. When "verify" feature is enabled, apply > the same logic to files nested under unverified redirected dirs. > > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> > --- > fs/overlayfs/inode.c | 18 ++++++++++++++---- > fs/overlayfs/namei.c | 4 ++++ > fs/overlayfs/overlayfs.h | 4 ++++ > fs/overlayfs/util.c | 27 +++++++++++++++++++++++++++ > 4 files changed, 49 insertions(+), 4 deletions(-) > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c > index 00b6b294272a..1b53755bd86c 100644 > --- a/fs/overlayfs/inode.c > +++ b/fs/overlayfs/inode.c > @@ -105,12 +105,22 @@ int ovl_getattr(const struct path *path, struct kstat *stat, > * Lower hardlinks may be broken on copy up to different > * upper files, so we cannot use the lower origin st_ino > * for those different files, even for the same fs case. > + * > + * Similarly, several redirected dirs can point to the > + * same dir on a lower layer. With the "verify" feature, > + * we do not use the lower origin st_ino, if any parent > + * is redirected and we haven't verified that this > + * redirect is unique. > + * > * With inodes index enabled, it is safe to use st_ino > - * of an indexed hardlinked origin. The index validates > - * that the upper hardlink is not broken. > + * of an indexed origin. The index validates that the > + * upper hardlink is not broken and that a redirected > + * dir is the only redirect to that origin. > */ > - if (is_dir || lowerstat.nlink == 1 || > - ovl_test_flag(OVL_INDEX, d_inode(dentry))) > + if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) || > + ((is_dir || lowerstat.nlink == 1) && > + (!ovl_verify(dentry->d_sb) || > + !ovl_dentry_is_renamed(dentry)))) Won't this make st_ino change when an ancestor directory is renamed? Even if there is no "double redirect" that we are fearing? If so, than I think the cure is worse than the disease. Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
