From: Jan Kara <jack@suse.cz>
Date: Tue, 3 Jan 2023 09:56:56 +0100
Subject: [PATCH] udf: Preserve link count of system files
References: bsc#1012628
Patch-mainline: 6.2.3
Git-commit: fc8033a34a3ca7d23353e645e6dde5d364ac5f12

commit fc8033a34a3ca7d23353e645e6dde5d364ac5f12 upstream.

System files in UDF filesystem have link count 0. To not confuse VFS we
fudge the link count to be 1 when reading such inodes however we forget
to restore the link count of 0 when writing such inodes. Fix that.

CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/udf/inode.c | 9 +++++++--
 fs/udf/super.c | 1 +
 fs/udf/udf_i.h | 3 ++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 2517cdda..2bc0f369 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1373,6 +1373,7 @@ static int udf_read_inode(struct inode *inode, bool hidden_inode)
 		ret = -EIO;
 		goto out;
 	}
+	iinfo->i_hidden = hidden_inode;
 	iinfo->i_unique = 0;
 	iinfo->i_lenEAttr = 0;
 	iinfo->i_lenExtents = 0;
@@ -1708,8 +1709,12 @@ static int udf_update_inode(struct inode *inode, int do_sync)
 
 	if (S_ISDIR(inode->i_mode) && inode->i_nlink > 0)
 		fe->fileLinkCount = cpu_to_le16(inode->i_nlink - 1);
-	else
-		fe->fileLinkCount = cpu_to_le16(inode->i_nlink);
+	else {
+		if (iinfo->i_hidden)
+			fe->fileLinkCount = cpu_to_le16(0);
+		else
+			fe->fileLinkCount = cpu_to_le16(inode->i_nlink);
+	}
 
 	fe->informationLength = cpu_to_le64(inode->i_size);
 
diff --git a/fs/udf/super.c b/fs/udf/super.c
index 06eda817..241b40e8 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -147,6 +147,7 @@ static struct inode *udf_alloc_inode(struct super_block *sb)
 	ei->i_next_alloc_goal = 0;
 	ei->i_strat4096 = 0;
 	ei->i_streamdir = 0;
+	ei->i_hidden = 0;
 	init_rwsem(&ei->i_data_sem);
 	ei->cached_extent.lstart = -1;
 	spin_lock_init(&ei->i_extent_cache_lock);
diff --git a/fs/udf/udf_i.h b/fs/udf/udf_i.h
index 06ff7006..312b7c9e 100644
--- a/fs/udf/udf_i.h
+++ b/fs/udf/udf_i.h
@@ -44,7 +44,8 @@ struct udf_inode_info {
 	unsigned		i_use : 1;	/* unallocSpaceEntry */
 	unsigned		i_strat4096 : 1;
 	unsigned		i_streamdir : 1;
-	unsigned		reserved : 25;
+	unsigned		i_hidden : 1;	/* hidden system inode */
+	unsigned		reserved : 24;
 	__u8			*i_data;
 	struct kernel_lb_addr	i_locStreamdir;
 	__u64			i_lenStreams;
-- 
2.35.3