+ convert-struct-pid-count-to-refcount_t.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     Subject: kernel/pid.c: convert struct pid:count to refcount_t
has been added to the -mm tree.  Its filename is
     convert-struct-pid-count-to-refcount_t.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/convert-struct-pid-count-to-refcount_t.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/convert-struct-pid-count-to-refcount_t.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx>
Subject: kernel/pid.c: convert struct pid:count to refcount_t

struct pid's count is an atomic_t field used as a refcount.  Use
refcount_t for it which is basically atomic_t but does additional checking
to prevent use-after-free bugs.  No change in behavior if
CONFIG_REFCOUNT_FULL=n.

Link: http://lkml.kernel.org/r/20190327145331.215360-1-joel@xxxxxxxxxxxxxxxxx
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 include/linux/pid.h |    5 +++--
 kernel/pid.c        |    8 ++++----
 2 files changed, 7 insertions(+), 6 deletions(-)

--- a/include/linux/pid.h~convert-struct-pid-count-to-refcount_t
+++ a/include/linux/pid.h
@@ -3,6 +3,7 @@
 #define _LINUX_PID_H
 
 #include <linux/rculist.h>
+#include <linux/refcount.h>
 
 enum pid_type
 {
@@ -56,7 +57,7 @@ struct upid {
 
 struct pid
 {
-	atomic_t count;
+	refcount_t count;
 	unsigned int level;
 	/* lists of tasks that use this pid */
 	struct hlist_head tasks[PIDTYPE_MAX];
@@ -69,7 +70,7 @@ extern struct pid init_struct_pid;
 static inline struct pid *get_pid(struct pid *pid)
 {
 	if (pid)
-		atomic_inc(&pid->count);
+		refcount_inc(&pid->count);
 	return pid;
 }
 
--- a/kernel/pid.c~convert-struct-pid-count-to-refcount_t
+++ a/kernel/pid.c
@@ -37,7 +37,7 @@
 #include <linux/init_task.h>
 #include <linux/syscalls.h>
 #include <linux/proc_ns.h>
-#include <linux/proc_fs.h>
+#include <linux/refcount.h>
 #include <linux/sched/task.h>
 #include <linux/idr.h>
 
@@ -106,8 +106,8 @@ void put_pid(struct pid *pid)
 		return;
 
 	ns = pid->numbers[pid->level].ns;
-	if ((atomic_read(&pid->count) == 1) ||
-	     atomic_dec_and_test(&pid->count)) {
+	if ((refcount_read(&pid->count) == 1) ||
+	     refcount_dec_and_test(&pid->count)) {
 		kmem_cache_free(ns->pid_cachep, pid);
 		put_pid_ns(ns);
 	}
@@ -210,7 +210,7 @@ struct pid *alloc_pid(struct pid_namespa
 	}
 
 	get_pid_ns(ns);
-	atomic_set(&pid->count, 1);
+	refcount_set(&pid->count, 1);
 	for (type = 0; type < PIDTYPE_MAX; ++type)
 		INIT_HLIST_HEAD(&pid->tasks[type]);
 
_

Patches currently in -mm which might be from joel@xxxxxxxxxxxxxxxxx are

convert-struct-pid-count-to-refcount_t.patch