linux-kernel - [PATCH] ovl: inode reference leak in ovl_is

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Date:   Tue, 16 Jun 2020 13:46:47 +0900
From:   youngjun <her0gyugyu@...il.com>
To:     amir73il@...il.com
Cc:     Miklos Szeredi <miklos@...redi.hu>, linux-unionfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, youngjun <her0gyugyu@...il.com>
Subject: [PATCH] ovl: inode reference leak in ovl_is_inuse true case.

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.

Signed-off-by: youngjun <her0gyugyu@...il.com>
---
 fs/overlayfs/super.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 91476bc422f9..0396793dadb8 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1029,6 +1029,12 @@ static const struct xattr_handler *ovl_xattr_handlers[] = {
 	NULL
 };
 
+/*
+ * 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.
+ */
 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
 			  struct inode **ptrap, const char *name)
 {
@@ -1499,8 +1505,10 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 
 		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]);
-- 
2.17.1

Thank you for comment Amir. I modified patch as you said.