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From: Miklos Szeredi <miklos@szeredi.hu>
To: syzbot <syzbot+75eab84fd0af9e8bf66b@syzkaller.appspotmail.com>
Cc: linux-kernel@vger.kernel.org,
	overlayfs <linux-unionfs@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: [syzbot] WARNING in ovl_create_real
Date: Wed, 8 Sep 2021 10:05:29 +0200	[thread overview]
Message-ID: <CAJfpegvVL-U3_4rhnhAU15qMAH-6WBuvmhnPMUkr_423R_2TOA@mail.gmail.com> (raw)
In-Reply-To: <CAJfpegvOa5cT5eRTsaMtAJ0YfZ1ob_kuW-NNK-emu3ncp2pK7A@mail.gmail.com>

[-- Attachment #1: Type: text/plain, Size: 82 bytes --]

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
master

[-- Attachment #2: ovl-fix-warning-in-ovl_create_real.patch --]
[-- Type: text/x-patch, Size: 1683 bytes --]

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 1fefb2b8960e..2f4125399896 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -137,8 +137,7 @@ int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
 	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;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 3894f3347955..2cd5741c873b 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/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);
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 178daa5e82c9..265181c110ae 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -787,10 +787,14 @@ static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
 			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:

  parent reply	other threads:[~2021-09-08  8:05 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-31 10:36 syzbot
2021-09-07 14:03 ` Miklos Szeredi
2021-09-07 15:15   ` syzbot
2021-09-08  8:05   ` Miklos Szeredi [this message]
2021-09-08  8:26     ` syzbot

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