linux-kernel - [PATCH] exfat: use updated exfat

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Date:   Wed,  8 Jun 2022 11:04:08 +0900
From:   Sungjong Seo <sj1557.seo@...sung.com>
To:     linkinjeon@...nel.org
Cc:     sj1557.seo@...sung.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] exfat: use updated exfat_chain directly during renaming

In order for a file to access its own directory entry set,
exfat_inode_info(ei) has two copied values. One is ei->dir, which is
a snapshot of exfat_chain of the parent directory, and the other is
ei->entry, which is the offset of the start of the directory entry set
in the parent directory.

Since the parent directory can be updated after the snapshot point,
it should be used only for accessing one's own directory entry set.

However, as of now, during renaming, it could try to traverse or to
allocate clusters via snapshot values, it does not make sense.

This potential problem has been revealed when exfat_update_parent_info()
was removed by commit d8dad2588add ("exfat: fix referencing wrong parent
directory information after renaming"). However, I don't think it's good
idea to bring exfat_update_parent_info() back.

Instead, let's use the updated exfat_chain of parent directory diectly.

Fixes: d8dad2588add ("exfat: fix referencing wrong parent directory information after renaming")

Signed-off-by: Sungjong Seo <sj1557.seo@...sung.com>
---
 fs/exfat/namei.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
index 76acc3721951..c6eaf7e9ea74 100644
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -1198,7 +1198,9 @@ static int __exfat_rename(struct inode *old_parent_inode,
 		return -ENOENT;
 	}

-	exfat_chain_dup(&olddir, &ei->dir);
+	exfat_chain_set(&olddir, EXFAT_I(old_parent_inode)->start_clu,
+		EXFAT_B_TO_CLU_ROUND_UP(i_size_read(old_parent_inode), sbi),
+		EXFAT_I(old_parent_inode)->flags);
 	dentry = ei->entry;

 	ep = exfat_get_dentry(sb, &olddir, dentry, &old_bh);
-- 
2.25.1