overlayfs update for 5.16

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Merge tag 'ovl-update-5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:

 - Fix a regression introduced in the last cycle

 - Fix a use-after-free in the AIO path

 - Fix a bogus warning reported by syzbot

* tag 'ovl-update-5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: fix filattr copy-up failure
  ovl: fix warning in ovl_create_real()
  ovl: fix use after free in struct ovl_aio_req

fs/overlayfs/copy_up.c

@@ -140,12 +140,14 @@ static int ovl_copy_fileattr(struct inode *inode, struct path *old,
 	int err;
 
 	err = ovl_real_fileattr_get(old, &oldfa);
-	if (err)
-		return err;
-
-	err = ovl_real_fileattr_get(new, &newfa);
-	if (err)
+	if (err) {
+		/* Ntfs-3g returns -EINVAL for "no fileattr support" */
+		if (err == -ENOTTY || err == -EINVAL)
+			return 0;
+		pr_warn("failed to retrieve lower fileattr (%pd2, err=%i)\n",
+			old, err);
 		return err;
+	}
 
 	/*
 	 * We cannot set immutable and append-only flags on upper inode,
@@ -159,6 +161,17 @@ static int ovl_copy_fileattr(struct inode *inode, struct path *old,
 			return err;
 	}
 
+	/* Don't bother copying flags if none are set */
+	if (!(oldfa.flags & OVL_COPY_FS_FLAGS_MASK))
+		return 0;
+
+	err = ovl_real_fileattr_get(new, &newfa);
+	if (err) {
+		pr_warn("failed to retrieve upper fileattr (%pd2, err=%i)\n",
+			new, err);
+		return err;
+	}
+
 	BUILD_BUG_ON(OVL_COPY_FS_FLAGS_MASK & ~FS_COMMON_FL);
 	newfa.flags &= ~OVL_COPY_FS_FLAGS_MASK;
 	newfa.flags |= (oldfa.flags & OVL_COPY_FS_FLAGS_MASK);

fs/overlayfs/dir.c

@@ -137,8 +137,7 @@ kill_whiteout:
 	goto out;
 }
 
-static int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry,
-			  umode_t mode)
+int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry, umode_t mode)
 {
 	int err;
 	struct dentry *d, *dentry = *newdentry;

fs/overlayfs/file.c

@@ -17,6 +17,7 @@
 
 struct ovl_aio_req {
 	struct kiocb iocb;
+	refcount_t ref;
 	struct kiocb *orig_iocb;
 	struct fd fd;
 };
@@ -252,6 +253,14 @@ static rwf_t ovl_iocb_to_rwf(int ifl)
 	return flags;
 }
 
+static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
+{
+	if (refcount_dec_and_test(&aio_req->ref)) {
+		fdput(aio_req->fd);
+		kmem_cache_free(ovl_aio_request_cachep, aio_req);
+	}
+}
+
 static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 {
 	struct kiocb *iocb = &aio_req->iocb;
@@ -268,8 +277,7 @@ static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 	}
 
 	orig_iocb->ki_pos = iocb->ki_pos;
-	fdput(aio_req->fd);
-	kmem_cache_free(ovl_aio_request_cachep, aio_req);
+	ovl_aio_put(aio_req);
 }
 
 static void ovl_aio_rw_complete(struct kiocb *iocb, long res)
@@ -319,7 +327,9 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 		aio_req->orig_iocb = iocb;
 		kiocb_clone(&aio_req->iocb, iocb, real.file);
 		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+		refcount_set(&aio_req->ref, 2);
 		ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
+		ovl_aio_put(aio_req);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
 	}
@@ -390,7 +400,9 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 		kiocb_clone(&aio_req->iocb, iocb, real.file);
 		aio_req->iocb.ki_flags = ifl;
 		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+		refcount_set(&aio_req->ref, 2);
 		ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
+		ovl_aio_put(aio_req);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
 	}

fs/overlayfs/inode.c

@@ -610,7 +610,10 @@ int ovl_real_fileattr_get(struct path *realpath, struct fileattr *fa)
 	if (err)
 		return err;
 
-	return vfs_fileattr_get(realpath->dentry, fa);
+	err = vfs_fileattr_get(realpath->dentry, fa);
+	if (err == -ENOIOCTLCMD)
+		err = -ENOTTY;
+	return err;
 }
 
 int ovl_fileattr_get(struct dentry *dentry, struct fileattr *fa)

fs/overlayfs/overlayfs.h

@@ -570,6 +570,7 @@ struct ovl_cattr {
 
 #define OVL_CATTR(m) (&(struct ovl_cattr) { .mode = (m) })
 
+int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry, umode_t mode);
 struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
 			       struct ovl_cattr *attr);
 int ovl_cleanup(struct inode *dir, struct dentry *dentry);

fs/overlayfs/super.c

@@ -787,10 +787,14 @@ retry:
 			goto retry;
 		}
 
-		work = ovl_create_real(dir, work, OVL_CATTR(attr.ia_mode));
-		err = PTR_ERR(work);
-		if (IS_ERR(work))
-			goto out_err;
+		err = ovl_mkdir_real(dir, &work, attr.ia_mode);
+		if (err)
+			goto out_dput;
+
+		/* Weird filesystem returning with hashed negative (kernfs)? */
+		err = -EINVAL;
+		if (d_really_is_negative(work))
+			goto out_dput;
 
 		/*
 		 * Try to remove POSIX ACL xattrs from workdir.  We are good if: