On 2017/2/15 2:03, Jaegeuk Kim wrote:
> VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation.
> But, if there is a race condition, f2fs_add_link() can be called multiple
> times, resulting in multiple dentries with a same name. This patches fixes
> it by adding __f2fs_find_entry() in f2fs_add_link() path.
As during ->lookup, i_mutex will be held all the time, so there is no race
condition in between different file creators?
Thanks,
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> ---
> fs/f2fs/dir.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> index 827c5daef4fc..bc7c48839bec 100644
> --- a/fs/f2fs/dir.c
> +++ b/fs/f2fs/dir.c
> @@ -643,14 +643,24 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name,
> struct inode *inode, nid_t ino, umode_t mode)
> {
> struct fscrypt_name fname;
> + struct page *page;
> + struct f2fs_dir_entry *de;
> int err;
>
> err = fscrypt_setup_filename(dir, name, 0, &fname);
> if (err)
> return err;
>
> - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode);
> -
> + de = __f2fs_find_entry(dir, &fname, &page);
> + if (de) {
> + f2fs_dentry_kunmap(dir, page);
> + f2fs_put_page(page, 0);
> + err = -EEXIST;
> + } else if (!IS_ERR(page)) {
> + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode);
> + } else {
> + err = PTR_ERR(page);
> + }
> fscrypt_free_filename(&fname);
> return err;
> }
>