1 files changed, 62 insertions, 6 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 9a3c251d033d..d32b5afa99dc 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -5004,6 +5004,40 @@ static int statmount_fs_type(struct kstatmount *s, struct seq_file *seq)
 	return 0;
 }
 
+static void statmount_fs_subtype(struct kstatmount *s, struct seq_file *seq)
+{
+	struct super_block *sb = s->mnt->mnt_sb;
+
+	if (sb->s_subtype)
+		seq_puts(seq, sb->s_subtype);
+}
+
+static int statmount_sb_source(struct kstatmount *s, struct seq_file *seq)
+{
+	struct super_block *sb = s->mnt->mnt_sb;
+	struct mount *r = real_mount(s->mnt);
+
+	if (sb->s_op->show_devname) {
+		size_t start = seq->count;
+		int ret;
+
+		ret = sb->s_op->show_devname(seq, s->mnt->mnt_root);
+		if (ret)
+			return ret;
+
+		if (unlikely(seq_has_overflowed(seq)))
+			return -EAGAIN;
+
+		/* Unescape the result */
+		seq->buf[seq->count] = '\0';
+		seq->count = start;
+		seq_commit(seq, string_unescape_inplace(seq->buf + start, UNESCAPE_OCTAL));
+	} else if (r->mnt_devname) {
+		seq_puts(seq, r->mnt_devname);
+	}
+	return 0;
+}
+
 static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns)
 {
 	s->sm.mask |= STATMOUNT_MNT_NS_ID;
@@ -5040,33 +5074,48 @@ static int statmount_mnt_opts(struct kstatmount *s, struct seq_file *seq)
 
 static int statmount_string(struct kstatmount *s, u64 flag)
 {
-	int ret;
+	int ret = 0;
 	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;
+	case STATMOUNT_FS_SUBTYPE:
+		sm->fs_subtype = start;
+		statmount_fs_subtype(s, seq);
+		break;
+	case STATMOUNT_SB_SOURCE:
+		sm->sb_source = start;
+		ret = statmount_sb_source(s, seq);
+		break;
 	default:
 		WARN_ON_ONCE(true);
 		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)
@@ -5201,6 +5250,12 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
 	if (!err && s->mask & STATMOUNT_MNT_OPTS)
 		err = statmount_string(s, STATMOUNT_MNT_OPTS);
 
+	if (!err && s->mask & STATMOUNT_FS_SUBTYPE)
+		err = statmount_string(s, STATMOUNT_FS_SUBTYPE);
+
+	if (!err && s->mask & STATMOUNT_SB_SOURCE)
+		err = statmount_string(s, STATMOUNT_SB_SOURCE);
+
 	if (!err && s->mask & STATMOUNT_MNT_NS_ID)
 		statmount_mnt_ns_id(s, ns);
 
@@ -5222,7 +5277,8 @@ 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_TYPE | STATMOUNT_MNT_OPTS | \
+			      STATMOUNT_FS_SUBTYPE | STATMOUNT_SB_SOURCE)
 
 static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,
 			      struct statmount __user *buf, size_t bufsize,