linux-kernel - [PATCH 4.19 36/50] ovl: expand warning in ovl_d

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Message-Id: <20210222121026.317653245@linuxfoundation.org>
Date:   Mon, 22 Feb 2021 13:13:27 +0100
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 4.19 36/50] ovl: expand warning in ovl_d_real()

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

commit cef4cbff06fbc3be54d6d79ee139edecc2ee8598 upstream.

There was a syzbot report with this warning but insufficient information...

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/overlayfs/super.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -82,7 +82,7 @@ static void ovl_dentry_release(struct de
 static struct dentry *ovl_d_real(struct dentry *dentry,
 				 const struct inode *inode)
 {
-	struct dentry *real;
+	struct dentry *real = NULL, *lower;
 
 	/* It's an overlay file */
 	if (inode && d_inode(dentry) == inode)
@@ -101,9 +101,10 @@ static struct dentry *ovl_d_real(struct
 	if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
 		return real;
 
-	real = ovl_dentry_lowerdata(dentry);
-	if (!real)
+	lower = ovl_dentry_lowerdata(dentry);
+	if (!lower)
 		goto bug;
+	real = lower;
 
 	/* Handle recursion */
 	real = d_real(real, inode);
@@ -111,8 +112,10 @@ static struct dentry *ovl_d_real(struct
 	if (!inode || inode == d_inode(real))
 		return real;
 bug:
-	WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
-	     inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
+	WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n",
+	     __func__, dentry, inode ? inode->i_sb->s_id : "NULL",
+	     inode ? inode->i_ino : 0, real,
+	     real && d_inode(real) ? d_inode(real)->i_ino : 0);
 	return dentry;
 }