[PATCH 01/18] fs: add two trivial lookup helpers

[PATCH 01/18] fs: add two trivial lookup helpers

[Christian Brauner]

Similar to the addition of lookup_one() add a version of
lookup_one_unlocked() and lookup_one_positive_unlocked() that take
idmapped mounts into account. This is required to port overlay to
support idmapped base layers.

Cc: <linux-fsdevel@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
 fs/namei.c            | 52 ++++++++++++++++++++++++++++++++++---------
 include/linux/namei.h |  2 ++
 2 files changed, 44 insertions(+), 10 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 3f1829b3ab5b..ca2a490a1f6b 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2768,7 +2768,8 @@ struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name,
 EXPORT_SYMBOL(lookup_one);
 
 /**
- * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
+ * lookup_one_unlocked - filesystem helper to lookup single pathname component
+ * @mnt_userns:	idmapping of the mount the lookup is performed from
  * @name:	pathname component to lookup
  * @base:	base directory to lookup from
  * @len:	maximum length @len should be interpreted to
@@ -2779,14 +2780,15 @@ EXPORT_SYMBOL(lookup_one);
  * Unlike lookup_one_len, it should be called without the parent
  * i_mutex held, and will take the i_mutex itself if necessary.
  */
-struct dentry *lookup_one_len_unlocked(const char *name,
-				       struct dentry *base, int len)
+struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns,
+				   const char *name, struct dentry *base,
+				   int len)
 {
 	struct qstr this;
 	int err;
 	struct dentry *ret;
 
-	err = lookup_one_common(&init_user_ns, name, base, len, &this);
+	err = lookup_one_common(mnt_userns, name, base, len, &this);
 	if (err)
 		return ERR_PTR(err);
 
@@ -2795,6 +2797,41 @@ struct dentry *lookup_one_len_unlocked(const char *name,
 		ret = lookup_slow(&this, base, 0);
 	return ret;
 }
+EXPORT_SYMBOL(lookup_one_unlocked);
+
+/*
+ * Like lookup_positive_unlocked() but takes a mount's idmapping into account.
+ */
+struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
+					    const char *name,
+					    struct dentry *base, int len)
+{
+	struct dentry *ret = lookup_one_unlocked(mnt_userns, name, base, len);
+	if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
+		dput(ret);
+		ret = ERR_PTR(-ENOENT);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(lookup_one_positive_unlocked);
+
+/**
+ * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
+ * @name:	pathname component to lookup
+ * @base:	base directory to lookup from
+ * @len:	maximum length @len should be interpreted to
+ *
+ * Note that this routine is purely a helper for filesystem usage and should
+ * not be called by generic code.
+ *
+ * Unlike lookup_one_len, it should be called without the parent
+ * i_mutex held, and will take the i_mutex itself if necessary.
+ */
+struct dentry *lookup_one_len_unlocked(const char *name,
+				       struct dentry *base, int len)
+{
+	return lookup_one_unlocked(&init_user_ns, name, base, len);
+}
 EXPORT_SYMBOL(lookup_one_len_unlocked);
 
 /*
@@ -2808,12 +2845,7 @@ EXPORT_SYMBOL(lookup_one_len_unlocked);
 struct dentry *lookup_positive_unlocked(const char *name,
 				       struct dentry *base, int len)
 {
-	struct dentry *ret = lookup_one_len_unlocked(name, base, len);
-	if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
-		dput(ret);
-		ret = ERR_PTR(-ENOENT);
-	}
-	return ret;
+	return lookup_one_positive_unlocked(&init_user_ns, name, base, len);
 }
 EXPORT_SYMBOL(lookup_positive_unlocked);
 
diff --git a/include/linux/namei.h b/include/linux/namei.h
index e89329bb3134..759b996b9e1a 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -69,6 +69,8 @@ extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
 extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
 extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
 struct dentry *lookup_one(struct user_namespace *, const char *, struct dentry *, int);
+struct dentry *lookup_one_unlocked(struct user_namespace *, const char *, struct dentry *, int);
+struct dentry *lookup_one_positive_unlocked(struct user_namespace *, const char *, struct dentry *, int);
 
 extern int follow_down_one(struct path *);
 extern int follow_down(struct path *);
-- 
2.32.0

[PATCH 02/18] exportfs: support idmapped mounts

[Christian Brauner]

Make the two locations where exportfs helpers check permission to lookup
a given inode idmapped mount aware by switching it to the lookup_one()
helper. This is a bugfix for the open_by_handle_at() system call which
doesn't take idmapped mounts into account currently. It's not tied to a
specific commit so we'll just Cc stable.

In addition this is required to support idmapped base layers in overlay.
The overlay filesystem uses exportfs to encode and decode file handles
for its index=on mount option and when nfs_export=on.

Cc: <stable@vger.kernel.org>
Cc: <linux-fsdevel@vger.kernel.org>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
---
 fs/exportfs/expfs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 0106eba46d5a..3ef80d000e13 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -145,7 +145,7 @@ static struct dentry *reconnect_one(struct vfsmount *mnt,
 	if (err)
 		goto out_err;
 	dprintk("%s: found name: %s\n", __func__, nbuf);
-	tmp = lookup_one_len_unlocked(nbuf, parent, strlen(nbuf));
+	tmp = lookup_one_unlocked(mnt_user_ns(mnt), nbuf, parent, strlen(nbuf));
 	if (IS_ERR(tmp)) {
 		dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp));
 		err = PTR_ERR(tmp);
@@ -525,7 +525,8 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
 		}
 
 		inode_lock(target_dir->d_inode);
-		nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
+		nresult = lookup_one(mnt_user_ns(mnt), nbuf,
+				     target_dir, strlen(nbuf));
 		if (!IS_ERR(nresult)) {
 			if (unlikely(nresult->d_inode != result->d_inode)) {
 				dput(nresult);
-- 
2.32.0