linux-kernel - [PATCH 4.6 96/96] vfs: fix deadlock in file_remove

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Message-Id: <20160808180248.124257479@linuxfoundation.org>
Date:	Mon,  8 Aug 2016 21:11:59 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Miklos Szeredi <mszeredi@...hat.com>
Subject: [PATCH 4.6 96/96] vfs: fix deadlock in file_remove_privs() on overlayfs

4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@...hat.com>

commit c1892c37769cf89c7e7ba57528ae2ccb5d153c9b upstream.

file_remove_privs() is called with inode lock on file_inode(), which
proceeds to calling notify_change() on file->f_path.dentry.  Which triggers
the WARN_ON_ONCE(!inode_is_locked(inode)) in addition to deadlocking later
when ovl_setattr tries to lock the underlying inode again.

Fix this mess by not mixing the layers, but doing everything on underlying
dentry/inode.

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Fixes: 07a2daab49c5 ("ovl: Copy up underlying inode's ->i_mode to overlay inode")
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/inode.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1739,8 +1739,8 @@ static int __remove_privs(struct dentry
  */
 int file_remove_privs(struct file *file)
 {
-	struct dentry *dentry = file->f_path.dentry;
-	struct inode *inode = d_inode(dentry);
+	struct dentry *dentry = file_dentry(file);
+	struct inode *inode = file_inode(file);
 	int kill;
 	int error = 0;
 
@@ -1748,7 +1748,7 @@ int file_remove_privs(struct file *file)
 	if (IS_NOSEC(inode))
 		return 0;
 
-	kill = file_needs_remove_privs(file);
+	kill = dentry_needs_remove_privs(dentry);
 	if (kill < 0)
 		return kill;
 	if (kill)