Re: [PATCH v2] ext4: replace strcpy() with '.' assignment

Kees Cook
2025-05-19T13:52:17Z

On Sun, May 18, 2025 at 11:54:21PM -0400, Ethan Carter Edwards wrote:
> strcpy() is deprecated; assignment can be used instead which
> theoretically/potentially increases speed as a function call is removed.
>
> Straight assignment works because the strings are not null-terminated
> which means they don't strictly require a str(s)cpy call.
>
> No functional changes intended.
>
> Link: https://github.com/KSPP/linux/issues/88
> Suggested-by: Theodore Ts'o <tytso@mit.edu>
> Signed-off-by: Ethan Carter Edwards <ethan@ethancedwards.com>
> ---
> There's an ongoing effort to remove calls to strcpy throughout the
> kernel.
>
> Link: https://github.com/KSPP/linux/issues/88
> ---
> Changes in v2:
> - completely remove the call to strcpy and replace it with assignment
> off of Theo's suggestion. Thanks.
> - Link to v1: https://lore.kernel.org/r/20250518-ext4-strcpy-v1-1-6c8a82ff078f@ethancedwards.com
> ---
> fs/ext4/inline.c | 4 ++--
> fs/ext4/namei.c | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
> index 2c9b762925c72f2ff5a402b02500370bc1eb0eb1..f3bc8b3904a8a9b55162f002b5bd63a527b290a5 100644
> --- a/fs/ext4/inline.c
> +++ b/fs/ext4/inline.c
> @@ -1314,7 +1314,7 @@ int ext4_inlinedir_to_tree(struct file *dir_file,
> if (pos == 0) {
> fake.inode = cpu_to_le32(inode->i_ino);
> fake.name_len = 1;
> - strcpy(fake.name, ".");
> + fake.name[0] = ".";

This means the trailing NUL byte isn't being copied any more? That seems
like a big change, even if name_len is being used for length tracking.

--
Kees Cook