On Thu, Jan 4, 2024 at 10:55 PM Chuck Lever <cel@xxxxxxxxxx> wrote:
>
> From: Chuck Lever <chuck.lever@xxxxxxxxxx>
>
> De-duplicate the same functionality in several places by hoisting
> the is_dot_dotdot() utility function into linux/fs.h.
>
> Suggested-by: Amir Goldstein <amir73il@xxxxxxxxx>
> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/crypto/fname.c | 8 +-------
> fs/ecryptfs/crypto.c | 10 ----------
> fs/exportfs/expfs.c | 4 +---
> fs/f2fs/f2fs.h | 11 -----------
> fs/namei.c | 6 ++----
> include/linux/fs.h | 13 +++++++++++++
> 6 files changed, 17 insertions(+), 35 deletions(-)
>
> diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
> index 7b3fc189593a..0ad52fbe51c9 100644
> --- a/fs/crypto/fname.c
> +++ b/fs/crypto/fname.c
> @@ -74,13 +74,7 @@ struct fscrypt_nokey_name {
>
> static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
> {
> - if (str->len == 1 && str->name[0] == '.')
> - return true;
> -
> - if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
> - return true;
> -
> - return false;
> + return is_dot_dotdot(str->name, str->len);
> }
>
> /**
> diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
> index 03bd55069d86..2fe0f3af1a08 100644
> --- a/fs/ecryptfs/crypto.c
> +++ b/fs/ecryptfs/crypto.c
> @@ -1949,16 +1949,6 @@ int ecryptfs_encrypt_and_encode_filename(
> return rc;
> }
>
> -static bool is_dot_dotdot(const char *name, size_t name_size)
> -{
> - if (name_size == 1 && name[0] == '.')
> - return true;
> - else if (name_size == 2 && name[0] == '.' && name[1] == '.')
> - return true;
> -
> - return false;
> -}
> -
> /**
> * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
> * @plaintext_name: The plaintext name
> diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
> index 84af58eaf2ca..07ea3d62b298 100644
> --- a/fs/exportfs/expfs.c
> +++ b/fs/exportfs/expfs.c
> @@ -255,9 +255,7 @@ static bool filldir_one(struct dir_context *ctx, const char *name, int len,
> container_of(ctx, struct getdents_callback, ctx);
>
> buf->sequence++;
> - /* Ignore the '.' and '..' entries */
> - if ((len > 2 || name[0] != '.' || (len == 2 && name[1] != '.')) &&
> - buf->ino == ino && len <= NAME_MAX) {
> + if (buf->ino == ino && len <= NAME_MAX && !is_dot_dotdot(name, len)) {
> memcpy(buf->name, name, len);
> buf->name[len] = '\0';
> buf->found = 1;
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 9043cedfa12b..322a3b8a3533 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -3368,17 +3368,6 @@ static inline bool f2fs_cp_error(struct f2fs_sb_info *sbi)
> return is_set_ckpt_flags(sbi, CP_ERROR_FLAG);
> }
>
> -static inline bool is_dot_dotdot(const u8 *name, size_t len)
> -{
> - if (len == 1 && name[0] == '.')
> - return true;
> -
> - if (len == 2 && name[0] == '.' && name[1] == '.')
> - return true;
> -
> - return false;
> -}
> -
> static inline void *f2fs_kmalloc(struct f2fs_sb_info *sbi,
> size_t size, gfp_t flags)
> {
> diff --git a/fs/namei.c b/fs/namei.c
> index 71c13b2990b4..2386a70667fa 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2667,10 +2667,8 @@ static int lookup_one_common(struct mnt_idmap *idmap,
> if (!len)
> return -EACCES;
>
> - if (unlikely(name[0] == '.')) {
> - if (len < 2 || (len == 2 && name[1] == '.'))
> - return -EACCES;
> - }
> + if (is_dot_dotdot(name, len))
> + return -EACCES;
>
> while (len--) {
> unsigned int c = *(const unsigned char *)name++;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 98b7a7a8c42e..53dd58a907e0 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2846,6 +2846,19 @@ extern bool path_is_under(const struct path *, const struct path *);
>
> extern char *file_path(struct file *, char *, int);
>
> +/**
> + * is_dot_dotdot - returns true only if @name is "." or ".."
> + * @name: file name to check
> + * @len: length of file name, in bytes
> + *
> + * Coded for efficiency.
> + */
> +static inline bool is_dot_dotdot(const char *name, size_t len)
> +{
> + return len && unlikely(name[0] == '.') &&
> + (len < 2 || (len == 2 && name[1] == '.'));
> +}
> +
Looking back at the version that I suggested, (len < 2
here is silly and should be (len == 1 || ...
But let's wait for inputs from other developers on this helper,
especially Al.
Thanks,
Amir.
