ovl: set i_ino to the value of st_ino for NFS export

Eddie Horng reported that readdir of an overlayfs directory that
was exported via NFSv3 returns entries with d_type set to DT_UNKNOWN.
The reason is that while preparing the response for readdirplus, nfsd
checks inside encode_entryplus_baggage() that a child dentry's inode
number matches the value of d_ino returns by overlayfs readdir iterator.

Because the overlayfs inodes use arbitrary inode numbers that are not
correlated with the values of st_ino/d_ino, NFSv3 falls back to not
encoding d_type. Although this is an allowed behavior, we can fix it for
the case of all overlayfs layers on the same underlying filesystem.

When NFS export is enabled and d_ino is consistent with st_ino
(samefs), set the same value also to i_ino in ovl_fill_inode() for all
overlayfs inodes, nfsd readdirplus sanity checks will pass.
ovl_fill_inode() may be called from ovl_new_inode(), before real inode
was created with ino arg 0. In that case, i_ino will be updated to real
upper inode i_ino on ovl_inode_init() or ovl_inode_update().

Reported-by: Eddie Horng <eddiehorng.tw@gmail.com>
Tested-by: Eddie Horng <eddiehorng.tw@gmail.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Fixes: 8383f1748829 ("ovl: wire up NFS export operations")
Cc: <stable@vger.kernel.org> #v4.16
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 3b1bd469accdfe767afc276def9f319f57ebde68..4689716f23d878f18df94b3e89ef94c6d5f99b37 100644 (file)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -459,9 +459,20 @@ static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
 #endif
 }
 
-static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
+static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev,
+                          unsigned long ino)
 {
-       inode->i_ino = get_next_ino();
+       /*
+        * When NFS export is enabled and d_ino is consistent with st_ino
+        * (samefs), set the same value to i_ino, because nfsd readdirplus
+        * compares d_ino values to i_ino values of child entries. When called
+        * from ovl_new_inode(), ino arg is 0, so i_ino will be updated to real
+        * upper inode i_ino on ovl_inode_init() or ovl_inode_update().
+        */
+       if (inode->i_sb->s_export_op && ovl_same_sb(inode->i_sb))
+               inode->i_ino = ino;
+       else
+               inode->i_ino = get_next_ino();
        inode->i_mode = mode;
        inode->i_flags |= S_NOCMTIME;
 #ifdef CONFIG_FS_POSIX_ACL
@@ -597,7 +608,7 @@ struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
 
        inode = new_inode(sb);
        if (inode)
-               ovl_fill_inode(inode, mode, rdev);
+               ovl_fill_inode(inode, mode, rdev, 0);
 
        return inode;
 }
@@ -710,6 +721,7 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
        struct inode *inode;
        bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry, index);
        bool is_dir;
+       unsigned long ino = 0;
 
        if (!realinode)
                realinode = d_inode(lowerdentry);
@@ -748,13 +760,14 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
                if (!is_dir)
                        nlink = ovl_get_nlink(lowerdentry, upperdentry, nlink);
                set_nlink(inode, nlink);
+               ino = key->i_ino;
        } else {
                /* Lower hardlink that will be broken on copy up */
                inode = new_inode(sb);
                if (!inode)
                        goto out_nomem;
        }
-       ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
+       ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev, ino);
        ovl_inode_init(inode, upperdentry, lowerdentry);
 
        if (upperdentry && ovl_is_impuredir(upperdentry))

diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 930784a266230ba4c51974ac681307aa7c82fbad..493f9b76fbf6460946e7671bd96e09f97dcc572c 100644 (file)
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -279,12 +279,16 @@ void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
                    struct dentry *lowerdentry)
 {
+       struct inode *realinode = d_inode(upperdentry ?: lowerdentry);
+
        if (upperdentry)
                OVL_I(inode)->__upperdentry = upperdentry;
        if (lowerdentry)
                OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
 
-       ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
+       ovl_copyattr(realinode, inode);
+       if (!inode->i_ino)
+               inode->i_ino = realinode->i_ino;
 }
 
 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
@@ -299,6 +303,8 @@ void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
        smp_wmb();
        OVL_I(inode)->__upperdentry = upperdentry;
        if (inode_unhashed(inode)) {
+               if (!inode->i_ino)
+                       inode->i_ino = upperinode->i_ino;
                inode->i_private = upperinode;
                __insert_inode_hash(inode, (unsigned long) upperinode);
        }