| From 29cb7f71220e5cc65addf37d39e8b9a410c6cf64 Mon Sep 17 00:00:00 2001 |
| From: Amir Goldstein <amir73il@gmail.com> |
| Date: Thu, 14 Nov 2019 22:28:41 +0200 |
| Subject: [PATCH] ovl: fix lookup failure on multi lower squashfs |
| |
| commit 7e63c87fc2dcf3be9d3aab82d4a0ea085880bdca upstream. |
| |
| 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. |
| |
| There is an unhandled corner case described by Miklos this way: |
| - two filesystems, A and B, both have null uuid |
| - upper layer is on A |
| - lower layer 1 is also on A |
| - lower layer 2 is on B |
| |
| In this case bad_uuid won't be set for B, because the check only |
| involves the list of lower fs. Hence we'll try to decode a layer 2 |
| origin on layer 1 and fail. |
| |
| We will deal with this corner case later. |
| |
| Reported-by: Colin Ian King <colin.king@canonical.com> |
| Tested-by: Colin Ian King <colin.king@canonical.com> |
| 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 <amir73il@gmail.com> |
| Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| 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..7621ff176d15 100644 |
| --- a/fs/overlayfs/super.c |
| +++ b/fs/overlayfs/super.c |
| @@ -1255,7 +1255,7 @@ 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)) |
| + if (!ofs->config.nfs_export && !ofs->upper_mnt) |
| return true; |
| |
| for (i = 0; i < ofs->numlowerfs; i++) { |
| @@ -1263,9 +1263,13 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) |
| * 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 +1281,7 @@ 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) |
| @@ -1288,11 +1293,15 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) |
| } |
| |
| if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) { |
| - 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", |
| - uuid_is_null(&sb->s_uuid) ? "null" : "conflicting", |
| - path->dentry); |
| + bad_uuid = true; |
| + if (ofs->config.index || ofs->config.nfs_export) { |
| + 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", |
| + uuid_is_null(&sb->s_uuid) ? "null" : |
| + "conflicting", |
| + path->dentry); |
| + } |
| } |
| |
| err = get_anon_bdev(&dev); |
| @@ -1303,6 +1312,7 @@ static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path) |
| |
| ofs->lower_fs[ofs->numlowerfs].sb = sb; |
| ofs->lower_fs[ofs->numlowerfs].pseudo_dev = dev; |
| + ofs->lower_fs[ofs->numlowerfs].bad_uuid = bad_uuid; |
| ofs->numlowerfs++; |
| |
| return ofs->numlowerfs; |
| -- |
| 2.7.4 |
| |