On Thu, 2024-11-14 at 16:31 +0100, Christian Brauner wrote:
> Add the ability to retrieve security mount options. Keep them separate
> from filesystem specific mount options so it's easy to tell them apart.
> Also allow to retrieve them separate from other mount options as most of
> the time users won't be interested in security specific mount options.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
> ---
> How do we feel about including this for v6.13 or should I rather delay it?
I say put it in. This is pretty straightforward stuff.
> ---
> fs/namespace.c | 74 ++++++++++++++++++++++++++++++--------
> include/uapi/linux/mount.h | 5 ++-
> 2 files changed, 64 insertions(+), 15 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index 4f39c4aba85d..a9065a9ab971 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -5072,13 +5072,30 @@ static int statmount_mnt_opts(struct kstatmount *s, struct seq_file *seq)
> return 0;
> }
>
> +static inline int statmount_opt_unescape(struct seq_file *seq, char *buf_start)
> +{
> + char *buf_end, *opt_start, *opt_end;
> + int count = 0;
> +
> + buf_end = seq->buf + seq->count;
> + *buf_end = '\0';
> + for (opt_start = buf_start + 1; opt_start < buf_end; opt_start = opt_end + 1) {
> + opt_end = strchrnul(opt_start, ',');
> + *opt_end = '\0';
> + buf_start += string_unescape(opt_start, buf_start, 0, UNESCAPE_OCTAL) + 1;
> + if (WARN_ON_ONCE(++count == INT_MAX))
> + return -EOVERFLOW;
> + }
> + seq->count = buf_start - 1 - seq->buf;
> + return count;
> +}
> +
> static int statmount_opt_array(struct kstatmount *s, struct seq_file *seq)
> {
> struct vfsmount *mnt = s->mnt;
> struct super_block *sb = mnt->mnt_sb;
> size_t start = seq->count;
> - char *buf_start, *buf_end, *opt_start, *opt_end;
> - u32 count = 0;
> + char *buf_start;
> int err;
>
> if (!sb->s_op->show_options)
> @@ -5095,17 +5112,39 @@ static int statmount_opt_array(struct kstatmount *s, struct seq_file *seq)
> if (seq->count == start)
> return 0;
>
> - buf_end = seq->buf + seq->count;
> - *buf_end = '\0';
> - for (opt_start = buf_start + 1; opt_start < buf_end; opt_start = opt_end + 1) {
> - opt_end = strchrnul(opt_start, ',');
> - *opt_end = '\0';
> - buf_start += string_unescape(opt_start, buf_start, 0, UNESCAPE_OCTAL) + 1;
> - if (WARN_ON_ONCE(++count == 0))
> - return -EOVERFLOW;
> - }
> - seq->count = buf_start - 1 - seq->buf;
> - s->sm.opt_num = count;
> + err = statmount_opt_unescape(seq, buf_start);
> + if (err < 0)
> + return err;
> +
> + s->sm.opt_num = err;
> + return 0;
> +}
> +
> +static int statmount_opt_sec_array(struct kstatmount *s, struct seq_file *seq)
> +{
> + struct vfsmount *mnt = s->mnt;
> + struct super_block *sb = mnt->mnt_sb;
> + size_t start = seq->count;
> + char *buf_start;
> + int err;
> +
> + buf_start = seq->buf + start;
> +
> + err = security_sb_show_options(seq, sb);
> + if (!err)
> + return err;
> +
> + if (unlikely(seq_has_overflowed(seq)))
> + return -EAGAIN;
> +
> + if (seq->count == start)
> + return 0;
> +
> + err = statmount_opt_unescape(seq, buf_start);
> + if (err < 0)
> + return err;
> +
> + s->sm.opt_sec_num = err;
> return 0;
> }
>
> @@ -5138,6 +5177,10 @@ static int statmount_string(struct kstatmount *s, u64 flag)
> sm->opt_array = start;
> ret = statmount_opt_array(s, seq);
> break;
> + case STATMOUNT_OPT_SEC_ARRAY:
> + sm->opt_sec_array = start;
> + ret = statmount_opt_sec_array(s, seq);
> + break;
> case STATMOUNT_FS_SUBTYPE:
> sm->fs_subtype = start;
> statmount_fs_subtype(s, seq);
> @@ -5294,6 +5337,9 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
> if (!err && s->mask & STATMOUNT_OPT_ARRAY)
> err = statmount_string(s, STATMOUNT_OPT_ARRAY);
>
> + if (!err && s->mask & STATMOUNT_OPT_SEC_ARRAY)
> + err = statmount_string(s, STATMOUNT_OPT_SEC_ARRAY);
> +
> if (!err && s->mask & STATMOUNT_FS_SUBTYPE)
> err = statmount_string(s, STATMOUNT_FS_SUBTYPE);
>
> @@ -5323,7 +5369,7 @@ static inline bool retry_statmount(const long ret, size_t *seq_size)
> #define STATMOUNT_STRING_REQ (STATMOUNT_MNT_ROOT | STATMOUNT_MNT_POINT | \
> STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | \
> STATMOUNT_FS_SUBTYPE | STATMOUNT_SB_SOURCE | \
> - STATMOUNT_OPT_ARRAY)
> + STATMOUNT_OPT_ARRAY | STATMOUNT_OPT_SEC_ARRAY)
>
> static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,
> struct statmount __user *buf, size_t bufsize,
> diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
> index c0fda4604187..c07008816aca 100644
> --- a/include/uapi/linux/mount.h
> +++ b/include/uapi/linux/mount.h
> @@ -177,7 +177,9 @@ struct statmount {
> __u32 sb_source; /* [str] Source string of the mount */
> __u32 opt_num; /* Number of fs options */
> __u32 opt_array; /* [str] Array of nul terminated fs options */
> - __u64 __spare2[47];
> + __u32 opt_sec_num; /* Number of security options */
> + __u32 opt_sec_array; /* [str] Array of nul terminated security options */
> + __u64 __spare2[46];
> char str[]; /* Variable size part containing strings */
> };
>
> @@ -214,6 +216,7 @@ struct mnt_id_req {
> #define STATMOUNT_FS_SUBTYPE 0x00000100U /* Want/got fs_subtype */
> #define STATMOUNT_SB_SOURCE 0x00000200U /* Want/got sb_source */
> #define STATMOUNT_OPT_ARRAY 0x00000400U /* Want/got opt_... */
> +#define STATMOUNT_OPT_SEC_ARRAY 0x00000800U /* Want/got opt_sec... */
>
> /*
> * Special @mnt_id values that can be passed to listmount
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
