ovl: fix EIO from lookup of non-indexed upper

Commit fbaf94ee3cd5 ("ovl: don't set origin on broken lower hardlink")
attempt to avoid the condition of non-indexed upper inode with lower
hardlink as origin. If this condition is found, lookup returns EIO.

The protection of commit mentioned above does not cover the case of lower
that is not a hardlink when it is copied up (with either index=off/on)
and then lower is hardlinked while overlay is offline.

Changes to lower layer while overlayfs is offline should not result in
unexpected behavior, so a permanent EIO error after creating a link in
lower layer should not be considered as correct behavior.

This fix replaces EIO error with success in cases where upper has origin
but no index is found, or index is found that does not match upper
inode. In those cases, lookup will not fail and the returned overlay inode
will be hashed by upper inode instead of by lower origin inode.

Fixes: 359f392ca53e ("ovl: lookup index entry for copy up origin")
Cc: <stable@vger.kernel.org> # v4.13
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index a619addecafcf05713b3a41e7e05a9e0866847a1..321511ed8c4235e102adfe84b98ac17c247eeadb 100644 (file)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -598,18 +598,30 @@ static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
        return true;
 }
 
-struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry)
+struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry,
+                           struct dentry *index)
 {
        struct dentry *lowerdentry = ovl_dentry_lower(dentry);
        struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL;
        struct inode *inode;
+       /* Already indexed or could be indexed on copy up? */
+       bool indexed = (index || (ovl_indexdir(dentry->d_sb) && !upperdentry));
+
+       if (WARN_ON(upperdentry && indexed && !lowerdentry))
+               return ERR_PTR(-EIO);
 
        if (!realinode)
                realinode = d_inode(lowerdentry);
 
-       if (!S_ISDIR(realinode->i_mode) &&
-           (upperdentry || (lowerdentry && ovl_indexdir(dentry->d_sb)))) {
-               struct inode *key = d_inode(lowerdentry ?: upperdentry);
+       /*
+        * Copy up origin (lower) may exist for non-indexed upper, but we must
+        * not use lower as hash key in that case.
+        * Hash inodes that are or could be indexed by origin inode and
+        * non-indexed upper inodes that could be hard linked by upper inode.
+        */
+       if (!S_ISDIR(realinode->i_mode) && (upperdentry || indexed)) {
+               struct inode *key = d_inode(indexed ? lowerdentry :
+                                                     upperdentry);
                unsigned int nlink;
 
                inode = iget5_locked(dentry->d_sb, (unsigned long) key,

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index e08164156cfe60777a2c47573547b4dca8fbd692..05e9a0ad5c081646c3471097031778d79af07419 100644 (file)
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -516,18 +516,9 @@ static struct dentry *ovl_lookup_index(struct dentry *dentry,
 
        inode = d_inode(index);
        if (d_is_negative(index)) {
-               if (upper && d_inode(origin)->i_nlink > 1) {
-                       pr_warn_ratelimited("overlayfs: hard link with origin but no index (ino=%lu).\n",
-                                           d_inode(origin)->i_ino);
-                       goto fail;
-               }
-
-               dput(index);
-               index = NULL;
+               goto out_dput;
        } else if (upper && d_inode(upper) != inode) {
-               pr_warn_ratelimited("overlayfs: wrong index found (index=%pd2, ino=%lu, upper ino=%lu).\n",
-                                   index, inode->i_ino, d_inode(upper)->i_ino);
-               goto fail;
+               goto out_dput;
        } else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) ||
                   ((inode->i_mode ^ d_inode(origin)->i_mode) & S_IFMT)) {
                /*
@@ -547,6 +538,11 @@ out:
        kfree(name.name);
        return index;
 
+out_dput:
+       dput(index);
+       index = NULL;
+       goto out;
+
 fail:
        dput(index);
        index = ERR_PTR(-EIO);
@@ -710,7 +706,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                upperdentry = dget(index);
 
        if (upperdentry || ctr) {
-               inode = ovl_get_inode(dentry, upperdentry);
+               inode = ovl_get_inode(dentry, upperdentry, index);
                err = PTR_ERR(inode);
                if (IS_ERR(inode))
                        goto out_free_oe;

diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index c706a6f999288136b567d75777f5f6742682a9a2..d9a0edd4e57e40c6157613a652d0dffe86335c07 100644 (file)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -286,7 +286,8 @@ int ovl_update_time(struct inode *inode, struct timespec *ts, int flags);
 bool ovl_is_private_xattr(const char *name);
 
 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev);
-struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry);
+struct inode *ovl_get_inode(struct dentry *dentry, struct dentry *upperdentry,
+                           struct dentry *index);
 static inline void ovl_copyattr(struct inode *from, struct inode *to)
 {
        to->i_uid = from->i_uid;