ubifs: ubifs_link: Fix wrong name len calculating when UBIFS is encrypted

The length of dentry name is calculated after the raw name is encrypted,
except for ubifs_link(), which could make the size of dir underflow.
Here is a reproducer:

 touch $TMP/file
 mkdir $TMP/dir
 stat $TMP/dir
 for i in $(seq 1 8)
 do
   ln $TMP/file $TMP/dir/$i
   unlink $TMP/dir/$i
 done
 stat $TMP/dir

The size of dir will be underflow(-96).

Fix it by calculating dentry name's length after the name is encrypted.

Fixes: f4f61d2cc6d8 ("ubifs: Implement encrypted filenames")
Reported-by: Roland Ruckerbauer <[email protected]>
Link: https://lore.kernel.org/linux-mtd/[email protected]/T/#u
Signed-off-by: Zhihao Cheng <[email protected]>
Signed-off-by: Richard Weinberger <[email protected]>

diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
index 2f48c58d47cdd02b18fbd6cd7b2439a34c42c89e..5dc1ac4d826def7c2f8de2c7c395a5e3cb9b657f 100644 (file)
--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -724,7 +724,7 @@ static int ubifs_link(struct dentry *old_dentry, struct inode *dir,
        struct inode *inode = d_inode(old_dentry);
        struct ubifs_inode *ui = ubifs_inode(inode);
        struct ubifs_inode *dir_ui = ubifs_inode(dir);
-       int err, sz_change = CALC_DENT_SIZE(dentry->d_name.len);
+       int err, sz_change;
        struct ubifs_budget_req req = { .new_dent = 1, .dirtied_ino = 2,
                                .dirtied_ino_d = ALIGN(ui->data_len, 8) };
        struct fscrypt_name nm;
@@ -748,6 +748,8 @@ static int ubifs_link(struct dentry *old_dentry, struct inode *dir,
        if (err)
                return err;
 
+       sz_change = CALC_DENT_SIZE(fname_len(&nm));
+
        err = dbg_check_synced_i_size(c, inode);
        if (err)
                goto out_fname;