[PATCH 6.12.y 5/6] exfat: fix incorrect directory checksum after rename to shorter name

[Sasha Levin <sashal@kernel.org>]

From: Chi Zhiling <chizhiling@kylinos.cn>

[ Upstream commit ff37797badd831797b8a27830fe5046d7e23fdc3 ]

When renaming a file in-place to a shorter name, exfat_remove_entries
marks excess entries as DELETED, but es->num_entries is not updated
accordingly. As a result, exfat_update_dir_chksum iterates over the
deleted entries and computes an incorrect checksum.

This does not lead to persistent corruption because mark_inode_dirty()
is called afterward, and __exfat_write_inode later recomputes the
checksum using the correct num_entries value.

Fix by setting es->num_entries = num_entries in exfat_init_ext_entry.

Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Stable-dep-of: 942296784b2a ("exfat: preserve benign secondary entries during rename and move")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/exfat/dir.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index 39310bb9eccc57..b6e700c8a9b043 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -507,6 +507,7 @@ void exfat_init_ext_entry(struct exfat_entry_set_cache *es, int num_entries,
 	unsigned short *uniname = p_uniname->name;
 	struct exfat_dentry *ep;
 
+	es->num_entries = num_entries;
 	ep = exfat_get_dentry_cached(es, ES_IDX_FILE);
 	ep->dentry.file.num_ext = (unsigned char)(num_entries - 1);
 
-- 
2.53.0