linux-kernel - [PATCH 5.7 179/244] ovl: inode reference leak in ovl_is

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Date:   Mon, 20 Jul 2020 17:37:30 +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, Amir Goldstein <amir73il@...il.com>,
        youngjun <her0gyugyu@...il.com>,
        Miklos Szeredi <mszeredi@...hat.com>
Subject: [PATCH 5.7 179/244] ovl: inode reference leak in ovl_is_inuse true case.

From: youngjun <her0gyugyu@...il.com>

commit 24f14009b8f1754ec2ae4c168940c01259b0f88a upstream.

When "ovl_is_inuse" true case, trap inode reference not put.  plus adding
the comment explaining sequence of ovl_is_inuse after ovl_setup_trap.

Fixes: 0be0bfd2de9d ("ovl: fix regression caused by overlapping layers detection")
Cc: <stable@...r.kernel.org> # v4.19+
Reviewed-by: Amir Goldstein <amir73il@...il.com>
Signed-off-by: youngjun <her0gyugyu@...il.com>
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/overlayfs/super.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1450,14 +1450,23 @@ static int ovl_get_layers(struct super_b
 		if (err < 0)
 			goto out;
 
+		/*
+		 * Check if lower root conflicts with this overlay layers before
+		 * checking if it is in-use as upperdir/workdir of "another"
+		 * mount, because we do not bother to check in ovl_is_inuse() if
+		 * the upperdir/workdir is in fact in-use by our
+		 * upperdir/workdir.
+		 */
 		err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir");
 		if (err)
 			goto out;
 
 		if (ovl_is_inuse(stack[i].dentry)) {
 			err = ovl_report_in_use(ofs, "lowerdir");
-			if (err)
+			if (err) {
+				iput(trap);
 				goto out;
+			}
 		}
 
 		mnt = clone_private_mount(&stack[i]);