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| author | Amir Goldstein <amir73il@gmail.com> | 2019-11-16 19:52:20 +0300 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-01-24 11:46:45 +0300 |
| commit | 1b81dddd354cf304574d79004400a6385613ae4e (patch) | |
| tree | cbd7bb2a96384c3ab2430e95ce5e0e8ccf67b5a3 | |
| parent | 07f1e59637a8e5a8bddba5da7567d46635da510f (diff) | |
| download | linux-1b81dddd354cf304574d79004400a6385613ae4e.tar.xz | |
ovl: fix corner case of conflicting lower layer uuid
This fixes ovl_lower_uuid_ok() to correctly detect the corner case:
- 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 would not have been set for B, because the check
only involved the list of lower fs. Hence we'll try to decode a layer 2
origin on layer 1 and fail.
We check for conflicting (and null) uuid among all lower layers, including
those layers that are on the same fs as the upper layer.
Reported-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
| -rw-r--r-- | fs/overlayfs/ovl_entry.h | 2 | ||||
| -rw-r--r-- | fs/overlayfs/super.c | 8 |
2 files changed, 8 insertions, 2 deletions
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h index d9fbebdb6076..c9324ad47e15 100644 --- a/fs/overlayfs/ovl_entry.h +++ b/fs/overlayfs/ovl_entry.h @@ -24,6 +24,8 @@ struct ovl_sb { dev_t pseudo_dev; /* Unusable (conflicting) uuid */ bool bad_uuid; + /* Used as a lower layer (but maybe also as upper) */ + bool is_lower; }; struct ovl_layer { diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index d7c406d8c793..7cf543608b9f 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1260,7 +1260,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) if (!ofs->config.nfs_export && !ofs->upper_mnt) return true; - for (i = 1; i < ofs->numfs; i++) { + for (i = 0; i < ofs->numfs; 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 @@ -1268,7 +1268,8 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) * if we detect multiple lower fs with the same uuid, we * disable lower file handle decoding on all of them. */ - if (uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) { + if (ofs->fs[i].is_lower && + uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) { ofs->fs[i].bad_uuid = true; return false; } @@ -1342,10 +1343,12 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, /* * All lower layers that share the same fs as upper layer, use the real * upper st_dev. + * is_lower will be set if upper fs is shared with a lower layer. */ if (ofs->upper_mnt) { ofs->fs[0].sb = ofs->upper_mnt->mnt_sb; ofs->fs[0].pseudo_dev = ofs->upper_mnt->mnt_sb->s_dev; + ofs->fs[0].is_lower = false; } for (i = 0; i < numlower; i++) { @@ -1387,6 +1390,7 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, ofs->layers[ofs->numlayer].fsid = fsid; ofs->layers[ofs->numlayer].fs = &ofs->fs[fsid]; ofs->numlayer++; + ofs->fs[fsid].is_lower = true; } /* |