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From: Amir Goldstein <amir73il@gmail.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Jeff Layton <jlayton@poochiereds.net>,
	"J . Bruce Fields" <bfields@fieldses.org>,
	linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [PATCH 02/14] ovl: grab i_count reference of lower inode
Date: Tue, 17 Oct 2017 19:44:19 +0300	[thread overview]
Message-ID: <1508258671-10800-3-git-send-email-amir73il@gmail.com> (raw)
In-Reply-To: <1508258671-10800-1-git-send-email-amir73il@gmail.com>

An overlay inode with elevated i_count may outlive its overlay dentry.
Since the only reference to OVL_I(inode)->lower was held by the lower
dentry object in the overlay dentry (oe->lowerstack[0]), releasing the
overlay dentry could leave a live inode with reference to freed lower
inode.

This may materialize to a bug when a disconnected dentry is obtained
from decoding an NFS file handle and a new allocated real inode has
the same address as the freed inode in OVL_I(inode)->lower, by which
the overlay inode is hashed.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/super.c | 1 +
 fs/overlayfs/util.c  | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index f3ad8107fec2..3c98991eebcd 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -197,6 +197,7 @@ static void ovl_destroy_inode(struct inode *inode)
 	struct ovl_inode *oi = OVL_I(inode);
 
 	dput(oi->__upperdentry);
+	iput(oi->lower);
 	kfree(oi->redirect);
 	ovl_dir_cache_free(inode);
 	mutex_destroy(&oi->lock);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index c668f9e26c3e..568ea4d4529d 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -260,7 +260,7 @@ void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
 	if (upperdentry)
 		OVL_I(inode)->__upperdentry = upperdentry;
 	if (lowerdentry)
-		OVL_I(inode)->lower = d_inode(lowerdentry);
+		OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
 
 	ovl_copyattr(d_inode(upperdentry ?: lowerdentry), inode);
 }
-- 
2.7.4

  parent reply	other threads:[~2017-10-17 16:44 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-17 16:44 [PATCH 00/14] Overlayfs NFS export support Amir Goldstein
2017-10-17 16:44 ` [PATCH 01/14] ovl: hash all overlay inodes for NFS export Amir Goldstein
2017-10-17 16:44 ` Amir Goldstein [this message]
2017-10-17 16:44 ` [PATCH 03/14] ovl: use d_splice_alias() in place of d_add() in lookup Amir Goldstein
2017-10-17 16:44 ` [PATCH 04/14] ovl: copy up of disconnected dentries Amir Goldstein
2017-10-17 16:44 ` [PATCH 05/14] ovl: encode/decode pure-upper non-connectable file handles Amir Goldstein
2017-10-17 16:44 ` [PATCH 06/14] ovl: encode pure-upper connectable " Amir Goldstein
2017-10-18 18:35   ` Amir Goldstein
2017-10-17 16:44 ` [PATCH 07/14] ovl: decode " Amir Goldstein
2017-10-17 16:44 ` [PATCH 08/14] ovl: encode/decode struct ovl_fh format " Amir Goldstein
2017-10-18 18:31   ` Amir Goldstein
2017-10-17 16:44 ` [PATCH 09/14] ovl: encode non-pure-upper non-connectable " Amir Goldstein
2017-10-17 16:44 ` [PATCH 10/14] ovl: obtain a non-pure-upper disconnected dentry Amir Goldstein
2017-10-17 16:44 ` [PATCH 11/14] ovl: decode non-pure-upper non-connectable file handles Amir Goldstein
2017-10-17 16:44 ` [PATCH 12/14] ovl: reconnect non-pure-upper dir " Amir Goldstein
2017-10-17 16:44 ` [PATCH 13/14] ovl: wire up NFS export support Amir Goldstein
2017-10-17 16:44 ` [PATCH 14/14] ovl: document NFS export Amir Goldstein
2017-10-18 18:43 ` [PATCH 00/14] Overlayfs NFS export support Amir Goldstein
2017-11-09 19:02 ` J . Bruce Fields
2017-11-09 19:20   ` Jeff Layton
2017-11-09 19:59   ` Amir Goldstein
2017-11-09 21:55     ` J . Bruce Fields

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