linux-kernel - [PATCH 2/2] ubifs: dirty_cow_znode: Fix memleak in error handling path

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Date:   Fri, 18 Nov 2022 17:02:36 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     <richard@....at>, <miquel.raynal@...tlin.com>,
        <s.hauer@...gutronix.de>
CC:     <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <chengzhihao1@...wei.com>, <yi.zhang@...wei.com>
Subject: [PATCH 2/2] ubifs: dirty_cow_znode: Fix memleak in error handling path

Following process will cause a memleak for copied up znode:

dirty_cow_znode
  zn = copy_znode(c, znode);
  err = insert_old_idx(c, zbr->lnum, zbr->offs);
  if (unlikely(err))
     return ERR_PTR(err);   // No one refers to zn.

Fix it by adding copied znode back to tnc, then it will be freed
by ubifs_destroy_tnc_subtree() while closing tnc.

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216705
Fixes: 1e51764a3c2a ("UBIFS: add new flash file system")
Signed-off-by: Zhihao Cheng <chengzhihao1@...wei.com>
---
 fs/ubifs/tnc.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
index 2df56bbc6865..2469f72eeaab 100644
--- a/fs/ubifs/tnc.c
+++ b/fs/ubifs/tnc.c
@@ -267,11 +267,18 @@ static struct ubifs_znode *dirty_cow_znode(struct ubifs_info *c,
 	if (zbr->len) {
 		err = insert_old_idx(c, zbr->lnum, zbr->offs);
 		if (unlikely(err))
-			return ERR_PTR(err);
+			/*
+			 * Obsolete znodes will be freed by tnc_destroy_cnext()
+			 * or free_obsolete_znodes(), copied up znodes should
+			 * be added back to tnc and freed by
+			 * ubifs_destroy_tnc_subtree().
+			 */
+			goto out;
 		err = add_idx_dirt(c, zbr->lnum, zbr->len);
 	} else
 		err = 0;
 
+out:
 	zbr->znode = zn;
 	zbr->lnum = 0;
 	zbr->offs = 0;
-- 
2.31.1