[RFC][PATCH] Pid namespaces vs locks interaction

[Vitaliy Gusev <vgusev@xxxxxxxxxx>]

Hello!
 
I am working on pid namespaces vs locks interaction and want to evaluate the 
idea.
fcntl(F_GETLK,..) can return pid of process for not current pid namespace (if 
process is belonged to the several namespaces). It is true also for pids 
in /proc/locks. So correct behavior is saving pointer to the struct pid of 
the process lock owner.

-- 
Thank,
Vitaliy Gusev

diff --git a/fs/locks.c b/fs/locks.c
index 8b8388e..d2d3d75 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -125,6 +125,7 @@
 #include <linux/syscalls.h>
 #include <linux/time.h>
 #include <linux/rcupdate.h>
+#include <linux/pid_namespace.h>
 
 #include <asm/semaphore.h>
 #include <asm/uaccess.h>
@@ -185,6 +186,7 @@ void locks_init_lock(struct file_lock *fl)
 	fl->fl_fasync = NULL;
 	fl->fl_owner = NULL;
 	fl->fl_pid = 0;
+	fl->fl_nspid = NULL;
 	fl->fl_file = NULL;
 	fl->fl_flags = 0;
 	fl->fl_type = 0;
@@ -553,6 +555,8 @@ static void locks_insert_lock(struct file_lock **pos, struct file_lock *fl)
 {
 	list_add(&fl->fl_link, &file_lock_list);
 
+	fl->fl_nspid = get_pid(task_tgid(current));
+
 	/* insert into file's list */
 	fl->fl_next = *pos;
 	*pos = fl;
@@ -584,6 +588,11 @@ static void locks_delete_lock(struct file_lock **thisfl_p)
 	if (fl->fl_ops && fl->fl_ops->fl_remove)
 		fl->fl_ops->fl_remove(fl);
 
+	if (fl->fl_nspid) {
+		put_pid(fl->fl_nspid);
+		fl->fl_nspid = NULL;
+	}
+
 	locks_wake_up_blocks(fl);
 	locks_free_lock(fl);
 }
@@ -673,14 +682,16 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
 		if (posix_locks_conflict(fl, cfl))
 			break;
 	}
-	if (cfl)
+	if (cfl) {
 		__locks_copy_lock(fl, cfl);
-	else
+		if (cfl->fl_nspid)
+			fl->fl_pid = pid_nr_ns(cfl->fl_nspid, 
+						task_active_pid_ns(current));
+	} else
 		fl->fl_type = F_UNLCK;
 	unlock_kernel();
 	return;
 }
-
 EXPORT_SYMBOL(posix_test_lock);
 
 /* This function tests for deadlock condition before putting a process to
@@ -2084,6 +2095,12 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 							int id, char *pfx)
 {
 	struct inode *inode = NULL;
+	unsigned int fl_pid;
+
+	if (fl->fl_nspid)
+		fl_pid = pid_nr_ns(fl->fl_nspid, task_active_pid_ns(current));
+	else
+		fl_pid = fl->fl_pid;
 
 	if (fl->fl_file != NULL)
 		inode = fl->fl_file->f_path.dentry->d_inode;
@@ -2124,16 +2141,16 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl,
 	}
 	if (inode) {
 #ifdef WE_CAN_BREAK_LSLK_NOW
-		seq_printf(f, "%d %s:%ld ", fl->fl_pid,
+		seq_printf(f, "%d %s:%ld ", fl_pid,
 				inode->i_sb->s_id, inode->i_ino);
 #else
 		/* userspace relies on this representation of dev_t ;-( */
-		seq_printf(f, "%d %02x:%02x:%ld ", fl->fl_pid,
+		seq_printf(f, "%d %02x:%02x:%ld ", fl_pid,
 				MAJOR(inode->i_sb->s_dev),
 				MINOR(inode->i_sb->s_dev), inode->i_ino);
 #endif
 	} else {
-		seq_printf(f, "%d <none>:0 ", fl->fl_pid);
+		seq_printf(f, "%d <none>:0 ", fl_pid);
 	}
 	if (IS_POSIX(fl)) {
 		if (fl->fl_end == OFFSET_MAX)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index b3ec4a4..5876f68 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -870,6 +870,7 @@ struct file_lock {
 	struct list_head fl_block;	/* circular list of blocked processes */
 	fl_owner_t fl_owner;
 	unsigned int fl_pid;
+	struct pid *fl_nspid;
 	wait_queue_head_t fl_wait;
 	struct file *fl_file;
 	unsigned char fl_flags;