[PATCH] fat: roll back the new entry when create/mkdir fails to build the inode

[zhoumin]

vfat_create(), vfat_mkdir(), msdos_create() and msdos_mkdir() add the
on-disk entry before calling fat_build_inode() to set up the VFS
inode.  If fat_build_inode() fails, the error is returned but the
entry stays on disk and the file or directory shows up after remount.

Remove the entry in that case.  For mkdir, also free the directory
cluster and decrement the parent's link count.

Signed-off-by: zhoumin <teczm@xxxxxxxxxxx>
---
 fs/fat/namei_msdos.c | 19 ++++++++++++++-----
 fs/fat/namei_vfat.c  | 19 ++++++++++++++-----
 2 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
index d46d1a3851f2..a0d1af5b8a5b 100644
--- a/fs/fat/namei_msdos.c
+++ b/fs/fat/namei_msdos.c
@@ -271,7 +271,7 @@ static int msdos_create(struct mnt_idmap *idmap, struct inode *dir,
 	struct fat_slot_info sinfo;
 	struct timespec64 ts;
 	unsigned char msdos_name[MSDOS_NAME];
-	int err, is_hid;
+	int err, err2, is_hid;
 
 	mutex_lock(&MSDOS_SB(sb)->s_lock);
 
@@ -292,11 +292,15 @@ static int msdos_create(struct mnt_idmap *idmap, struct inode *dir,
 	if (err)
 		goto out;
 	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
-	brelse(sinfo.bh);
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
+		err2 = fat_remove_entries(dir, &sinfo);
+		if (err2)
+			fat_msg(sb, KERN_WARNING,
+				"failed to roll back new entry (%d)", err2);
 		goto out;
 	}
+	brelse(sinfo.bh);
 	fat_truncate_time(inode, &ts, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
@@ -353,7 +357,7 @@ static struct dentry *msdos_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	struct inode *inode;
 	unsigned char msdos_name[MSDOS_NAME];
 	struct timespec64 ts;
-	int err, is_hid, cluster;
+	int err, err2, is_hid, cluster;
 
 	mutex_lock(&MSDOS_SB(sb)->s_lock);
 
@@ -381,12 +385,17 @@ static struct dentry *msdos_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	inc_nlink(dir);
 
 	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
-	brelse(sinfo.bh);
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
-		/* the directory was completed, just return a error */
+		err2 = fat_remove_entries(dir, &sinfo);
+		if (err2)
+			fat_msg(sb, KERN_WARNING,
+				"failed to roll back new entry (%d)", err2);
+		drop_nlink(dir);
+		fat_free_clusters(dir, cluster);
 		goto out;
 	}
+	brelse(sinfo.bh);
 	set_nlink(inode, 2);
 	fat_truncate_time(inode, &ts, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index da3e89c0b16a..31d83de5beaa 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -760,7 +760,7 @@ static int vfat_create(struct mnt_idmap *idmap, struct inode *dir,
 	struct inode *inode;
 	struct fat_slot_info sinfo;
 	struct timespec64 ts;
-	int err;
+	int err, err2;
 
 	mutex_lock(&MSDOS_SB(sb)->s_lock);
 
@@ -771,11 +771,15 @@ static int vfat_create(struct mnt_idmap *idmap, struct inode *dir,
 	inode_inc_iversion(dir);
 
 	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
-	brelse(sinfo.bh);
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
+		err2 = fat_remove_entries(dir, &sinfo);
+		if (err2)
+			fat_msg(sb, KERN_WARNING,
+				"failed to roll back new entry (%d)", err2);
 		goto out;
 	}
+	brelse(sinfo.bh);
 	inode_inc_iversion(inode);
 
 	d_instantiate(dentry, inode);
@@ -853,7 +857,7 @@ static struct dentry *vfat_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	struct inode *inode;
 	struct fat_slot_info sinfo;
 	struct timespec64 ts;
-	int err, cluster;
+	int err, err2, cluster;
 
 	mutex_lock(&MSDOS_SB(sb)->s_lock);
 
@@ -870,12 +874,17 @@ static struct dentry *vfat_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	inc_nlink(dir);
 
 	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
-	brelse(sinfo.bh);
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
-		/* the directory was completed, just return a error */
+		err2 = fat_remove_entries(dir, &sinfo);
+		if (err2)
+			fat_msg(sb, KERN_WARNING,
+				"failed to roll back new entry (%d)", err2);
+		drop_nlink(dir);
+		fat_free_clusters(dir, cluster);
 		goto out;
 	}
+	brelse(sinfo.bh);
 	inode_inc_iversion(inode);
 	set_nlink(inode, 2);
 
-- 
2.53.0