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charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 13, 2019 at 6:02 PM Miklos Szeredi wrote: > > On Thu, Nov 7, 2019 at 11:50 AM Colin King wrote: > > > > From: Colin Ian King > > > > In the past, overlayfs required that lower fs have non null uuid in > > order to support nfs export and decode copy up origin file handles. > > > > Commit 9df085f3c9a2 ("ovl: relax requirement for non null uuid of > > lower fs") relaxed this requirement for nfs export support, as long > > as uuid (even if null) is unique among all lower fs. > > > > However, said commit unintentionally also relaxed the non null uuid > > requirement for decoding copy up origin file handles, regardless of > > the unique uuid requirement. > > > > Amend this mistake by disabling decoding of copy up origin file handle > > from lower fs with a conflicting uuid. > > > > We still encode copy up origin file handles from those fs, because > > file handles like those already exist in the wild and because they > > might provide useful information in the future. > > > > Reported-by: Colin Ian King > > Link: https://lore.kernel.org/lkml/20191106234301.283006-1-colin.king@canonical.com/ > > Fixes: 9df085f3c9a2 ("ovl: relax requirement for non null uuid ...") > > Cc: stable@vger.kernel.org # v4.20+ > > Signed-off-by: Amir Goldstein > > Signed-off-by: Colin Ian King > > --- > > fs/overlayfs/namei.c | 8 ++++++++ > > fs/overlayfs/ovl_entry.h | 2 ++ > > fs/overlayfs/super.c | 16 ++++++++++------ > > 3 files changed, 20 insertions(+), 6 deletions(-) > > > > diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c > > index e9717c2f7d45..f47c591402d7 100644 > > --- a/fs/overlayfs/namei.c > > +++ b/fs/overlayfs/namei.c > > @@ -325,6 +325,14 @@ int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected, > > int i; > > > > for (i = 0; i < ofs->numlower; i++) { > > + /* > > + * If lower fs uuid is not unique among lower fs we cannot match > > + * fh->uuid to layer. > > + */ > > + if (ofs->lower_layers[i].fsid && > > + ofs->lower_layers[i].fs->bad_uuid) > > + continue; > > + > > origin = ovl_decode_real_fh(fh, ofs->lower_layers[i].mnt, > > connected); > > if (origin) > > diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h > > index a8279280e88d..28348c44ea5b 100644 > > --- a/fs/overlayfs/ovl_entry.h > > +++ b/fs/overlayfs/ovl_entry.h > > @@ -22,6 +22,8 @@ struct ovl_config { > > struct ovl_sb { > > struct super_block *sb; > > dev_t pseudo_dev; > > + /* Unusable (conflicting) uuid */ > > + bool bad_uuid; > > }; > > > > struct ovl_layer { > > diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c > > index afbcb116a7f1..5d4faab57ba0 100644 > > --- a/fs/overlayfs/super.c > > +++ b/fs/overlayfs/super.c > > @@ -1255,17 +1255,18 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) > > { > > unsigned int i; > > > > - if (!ofs->config.nfs_export && !(ofs->config.index && ofs->upper_mnt)) > > - return true; > > - Colin, I mislead you, this should be (I think): if (!ofs->config.nfs_export && !ofs->upper_mnt) return true; > > for (i = 0; i < ofs->numlowerfs; i++) { > > /* > > * We use uuid to associate an overlay lower file handle with a > > * lower layer, so we can accept lower fs with null uuid as long > > * as all lower layers with null uuid are on the same fs. > > + * if we detect multiple lower fs with the same uuid, we > > + * disable lower file handle decoding on all of them. > > */ > > - if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) > > + if (uuid_equal(&ofs->lower_fs[i].sb->s_uuid, uuid)) { > > + ofs->lower_fs[i].bad_uuid = true; > > return false; > > + } > > } > > return true; > > } > > @@ -1277,6 +1278,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) > > unsigned int i; > > dev_t dev; > > int err; > > + bool bad_uuid = false; > > > > /* fsid 0 is reserved for upper fs even with non upper overlay */ > > if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb == sb) > > @@ -1287,10 +1289,11 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) > > return i + 1; > > } > > > > - if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { > > + if (ofs->upper_mnt && !ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { > > This seems bogus: why only check conflicting lower layers if there's > an upper layer? It is bogus - it was my (wrong) suggestion. The thinking was that we only decode origin fh if we have an upper layer and index only valid with upper layer. I forgot the case of nfs_export and lower-only setup. Suggested fix above. > > > + bad_uuid = true; > > ofs->config.index = false; > > ofs->config.nfs_export = false; > > - pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', falling back to index=off,nfs_export=off.\n", > > + pr_warn("overlayfs: %s uuid detected in lower fs '%pd2', enforcing index=off,nfs_export=off.\n", > > And this while this makes sense, it doesn't really fit into this patch > (no change of behavior regarding how index and nfs_export are > handled). > Again, this was my (not wrong?) suggestion. What this patch changes is that ovl_lower_uuid_ok() can now return false and we get to this print although user did not ask for index nor nfs_export. So the "falling back" language no longer makes sense. Thanks, Amir.