On Mon 11-11-24 10:09:55, Jeff Layton wrote:
> When one of the statmount_string() handlers doesn't emit anything to
> seq, the kernel currently sets the corresponding flag and emits an empty
> string.
>
> Given that statmount() returns a mask of accessible fields, just leave
> the bit unset in this case, and skip any NULL termination. If nothing
> was emitted to the seq, then the EOVERFLOW and EAGAIN cases aren't
> applicable and the function can just return immediately.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/namespace.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index ba77ce1c6788dfe461814b5826fcbb3aab68fad4..28ad153b1fb6f49653c0a85d12da457c4650a87e 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -5046,22 +5046,23 @@ static int statmount_string(struct kstatmount *s, u64 flag)
> size_t kbufsize;
> struct seq_file *seq = &s->seq;
> struct statmount *sm = &s->sm;
> + u32 start = seq->count;
>
> switch (flag) {
> case STATMOUNT_FS_TYPE:
> - sm->fs_type = seq->count;
> + sm->fs_type = start;
> ret = statmount_fs_type(s, seq);
> break;
> case STATMOUNT_MNT_ROOT:
> - sm->mnt_root = seq->count;
> + sm->mnt_root = start;
> ret = statmount_mnt_root(s, seq);
> break;
> case STATMOUNT_MNT_POINT:
> - sm->mnt_point = seq->count;
> + sm->mnt_point = start;
> ret = statmount_mnt_point(s, seq);
> break;
> case STATMOUNT_MNT_OPTS:
> - sm->mnt_opts = seq->count;
> + sm->mnt_opts = start;
> ret = statmount_mnt_opts(s, seq);
> break;
> default:
> @@ -5069,6 +5070,12 @@ static int statmount_string(struct kstatmount *s, u64 flag)
> return -EINVAL;
> }
>
> + /*
> + * If nothing was emitted, return to avoid setting the flag
> + * and terminating the buffer.
> + */
> + if (seq->count == start)
> + return ret;
> if (unlikely(check_add_overflow(sizeof(*sm), seq->count, &kbufsize)))
> return -EOVERFLOW;
> if (kbufsize >= s->bufsize)
>
> --
> 2.47.0
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
