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))))
stat->ino = lowerstat.ino;
if (samefs)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 56deb2785af7..8aa4724d4fb0 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -811,6 +811,10 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
goto out_free_oe;
OVL_I(inode)->redirect = upperredirect;
+ /* OVL_RENAMED indicates rename in any layer/path component */
+ if (d.redirect ||
+ ovl_test_flag(OVL_RENAMED, d_inode(dentry->d_parent)))
+ ovl_set_flag(OVL_RENAMED, inode);
if (index)
ovl_set_flag(OVL_INDEX, inode);
}
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 379bb349acc4..46f9f097e822 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -33,7 +33,10 @@ enum ovl_flag {
OVL_IMPURE,
/* Non-merge dir that may contain whiteout entries */
OVL_WHITEOUTS,
+ /* Found index entry for origin inode */
OVL_INDEX,
+ /* Merge dir in path was redirected */
+ OVL_RENAMED,
};
/*
@@ -219,6 +222,7 @@ void ovl_dentry_set_upper_alias(struct dentry *dentry);
bool ovl_redirect_dir(struct super_block *sb);
const char *ovl_dentry_get_redirect(struct dentry *dentry);
void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect);
+bool ovl_dentry_is_renamed(struct dentry *dentry);
void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
struct dentry *lowerdentry);
void ovl_inode_update(struct inode *inode, struct dentry *upperdentry);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index fb0b561b0568..42809eae0992 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -256,6 +256,33 @@ void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
kfree(oi->redirect);
oi->redirect = redirect;
+ /* Descendant are marked RENAMED lazily by ovl_dentry_is_renamed() */
+ ovl_set_flag(OVL_RENAMED, d_inode(dentry));
+}
+
+/*
+ * Check if any component in path has been renamed.
+ */
+bool ovl_dentry_is_renamed(struct dentry *dentry)
+{
+ struct dentry *d, *tmp;
+ bool renamed;
+
+ for (d = dget(dentry); !IS_ROOT(d);) {
+ if (ovl_test_flag(OVL_RENAMED, d_inode(d)))
+ break;
+
+ tmp = dget_parent(d);
+ dput(d);
+ d = tmp;
+ }
+
+ renamed = !IS_ROOT(d);
+ dput(d);
+
+ if (renamed)
+ ovl_set_flag(OVL_RENAMED, d_inode(dentry));
+ return renamed;
}
void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
--
2.7.4
--
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