userns: Add kprojid_t and associated infrastructure in projid.h

Implement kprojid_t a cousin of the kuid_t and kgid_t.

The per user namespace mapping of project id values can be set with
/proc/<pid>/projid_map.

A full compliment of helpers is provided: make_kprojid, from_kprojid,
from_kprojid_munged, kporjid_has_mapping, projid_valid, projid_eq,
projid_eq, projid_lt.

Project identifiers are part of the generic disk quota interface,
although it appears only xfs implements project identifiers currently.

The xfs code allows anyone who has permission to set the project
identifier on a file to use any project identifier so when
setting up the user namespace project identifier mappings I do
not require a capability.

Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 138cff4b05dd..acd1960c28a2 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2991,6 +2991,11 @@ static int proc_gid_map_open(struct inode *inode, struct file *file)
 	return proc_id_map_open(inode, file, &proc_gid_seq_operations);
 }
 
+static int proc_projid_map_open(struct inode *inode, struct file *file)
+{
+	return proc_id_map_open(inode, file, &proc_projid_seq_operations);
+}
+
 static const struct file_operations proc_uid_map_operations = {
 	.open		= proc_uid_map_open,
 	.write		= proc_uid_map_write,
@@ -3006,6 +3011,14 @@ static const struct file_operations proc_gid_map_operations = {
 	.llseek		= seq_lseek,
 	.release	= proc_id_map_release,
 };
+
+static const struct file_operations proc_projid_map_operations = {
+	.open		= proc_projid_map_open,
+	.write		= proc_projid_map_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= proc_id_map_release,
+};
 #endif /* CONFIG_USER_NS */
 
 static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
@@ -3113,6 +3126,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 #ifdef CONFIG_USER_NS
 	REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
 	REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
+	REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
 #endif
 };
 
@@ -3476,6 +3490,7 @@ static const struct pid_entry tid_base_stuff[] = {
 #ifdef CONFIG_USER_NS
 	REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
 	REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
+	REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
 #endif
 };