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From: Miklos Szeredi <mszeredi@redhat.com>
To: linux-unionfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 07/11] ovl: make ovl_create_real() cope with vfs_mkdir() safely
Date: Tue, 29 May 2018 16:41:39 +0200	[thread overview]
Message-ID: <20180529144143.16378-8-mszeredi@redhat.com> (raw)
In-Reply-To: <20180529144143.16378-1-mszeredi@redhat.com>

From: Amir Goldstein <amir73il@gmail.com>

vfs_mkdir() may succeed and leave the dentry passed to it unhashed and
negative.  ovl_create_real() is the last caller breaking when that
happens.

[amir: split re-factoring of ovl_create_temp() to prep patch
       add comment about unhashed dir after mkdir
       add pr_warn() if mkdir succeeds and lookup fails]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/overlayfs/dir.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 1b181292a624..b33d37d1a87c 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -114,6 +114,37 @@ int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
 	goto out;
 }
 
+static struct dentry *ovl_mkdir_real(struct inode *dir, struct dentry *dentry,
+				     umode_t mode)
+{
+	int err;
+
+	err = ovl_do_mkdir(dir, dentry, mode);
+	if (err) {
+		dput(dentry);
+		return ERR_PTR(err);
+	}
+
+	/*
+	 * vfs_mkdir() may succeed and leave the dentry passed
+	 * to it unhashed and negative. If that happens, try to
+	 * lookup a new hashed and positive dentry.
+	 */
+	if (unlikely(d_unhashed(dentry))) {
+		struct dentry *d;
+
+		d = lookup_one_len(dentry->d_name.name, dentry->d_parent,
+				   dentry->d_name.len);
+		if (IS_ERR(d)) {
+			pr_warn("overlayfs: failed lookup after mkdir (%pd2, err=%i).\n",
+				dentry, err);
+		}
+		dput(dentry);
+		dentry = d;
+	}
+	return dentry;
+}
+
 struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
 			       struct ovl_cattr *attr)
 {
@@ -135,8 +166,8 @@ struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
 			break;
 
 		case S_IFDIR:
-			err = ovl_do_mkdir(dir, newdentry, attr->mode);
-			break;
+			/* mkdir is special... */
+			return ovl_mkdir_real(dir, newdentry, attr->mode);
 
 		case S_IFCHR:
 		case S_IFBLK:
-- 
2.14.3

  parent reply	other threads:[~2018-05-29 14:41 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-29 14:41 [PATCH 00/11] overlayfs fixes Miklos Szeredi
2018-05-29 14:41 ` [PATCH 01/11] ovl: update documentation for unionmount-testsuite Miklos Szeredi
2018-05-29 14:41 ` [PATCH 02/11] ovl: remove WARN_ON() real inode attributes mismatch Miklos Szeredi
2018-05-29 14:41 ` [PATCH 03/11] ovl: strip debug argument from ovl_do_ helpers Miklos Szeredi
2018-05-29 14:41 ` [PATCH 04/11] ovl: struct cattr cleanups Miklos Szeredi
2018-05-29 14:41 ` [PATCH 05/11] ovl: return dentry from ovl_create_real() Miklos Szeredi
2018-05-29 15:24   ` Amir Goldstein
2018-05-30  8:28     ` Miklos Szeredi
2018-05-29 14:41 ` [PATCH 06/11] ovl: create helper ovl_create_temp() Miklos Szeredi
2018-05-29 14:41 ` Miklos Szeredi [this message]
2018-05-29 15:29   ` [PATCH 07/11] ovl: make ovl_create_real() cope with vfs_mkdir() safely Amir Goldstein
2018-05-30  8:18     ` Miklos Szeredi
2018-05-29 14:41 ` [PATCH 08/11] ovl: clean up copy-up error paths Miklos Szeredi
2018-05-29 14:41 ` [PATCH 09/11] vfs: factor out inode_insert5() Miklos Szeredi
2018-06-10  5:49   ` Al Viro
2018-06-10  6:02     ` Al Viro
2018-06-11  9:15       ` Miklos Szeredi
2018-06-11 11:32         ` Miklos Szeredi
2018-06-11 16:43           ` Al Viro
2018-06-12 12:38             ` Miklos Szeredi
2018-05-29 14:41 ` [PATCH 10/11] ovl: Pass argument to ovl_get_inode() in a structure Miklos Szeredi
2018-05-29 14:41 ` [PATCH 11/11] ovl: use inode_insert5() to hash a newly created inode Miklos Szeredi

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