linux-kernel - [PATCH] hfs: fix potential use after free in hfs_correct_next_unused

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Message-ID: <aN-Xw8KnbSnuIcLk@stanley.mountain>
Date: Fri, 3 Oct 2025 12:30:43 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Viacheslav Dubeyko <slava@...eyko.com>
Cc: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
	Yangtao Li <frank.li@...o.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] hfs: fix potential use after free in
 hfs_correct_next_unused_CNID()

This code calls hfs_bnode_put(node) which drops the refcount and then
dreferences "node" on the next line.  It's only safe to use "node"
when we're holding a reference so flip these two lines around.

Fixes: a06ec283e125 ("hfs: add logic of correcting a next unused CNID")
Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
---
 fs/hfs/catalog.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/hfs/catalog.c b/fs/hfs/catalog.c
index caebabb6642f..b80ba40e3877 100644
--- a/fs/hfs/catalog.c
+++ b/fs/hfs/catalog.c
@@ -322,9 +322,9 @@ int hfs_correct_next_unused_CNID(struct super_block *sb, u32 cnid)
 			}
 		}
 
+		node_id = node->prev;
 		hfs_bnode_put(node);
 
-		node_id = node->prev;
 	} while (node_id >= leaf_head);
 
 	return -ENOENT;
-- 
2.51.0