The patch titled
Subject: userns: use refcount_t for reference counting instead atomic_t
has been added to the -mm tree. Its filename is
userns-use-refcount_t-for-reference-counting-instead-atomic_t.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userns-use-refcount_t-for-reference-counting-instead-atomic_t.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userns-use-refcount_t-for-reference-counting-instead-atomic_t.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
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------------------------------------------------------
From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Subject: userns: use refcount_t for reference counting instead atomic_t
refcount_t type and corresponding API should be used instead of atomic_t
wh en the variable is used as a reference counter. This avoids accidental
refcounter overflows that might lead to use-after-free situations.
Link: http://lkml.kernel.org/r/20180703200141.28415-6-bigeasy@xxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/sched/user.h | 5 +++--
kernel/user.c | 8 ++++----
2 files changed, 7 insertions(+), 6 deletions(-)
diff -puN include/linux/sched/user.h~userns-use-refcount_t-for-reference-counting-instead-atomic_t include/linux/sched/user.h
--- a/include/linux/sched/user.h~userns-use-refcount_t-for-reference-counting-instead-atomic_t
+++ a/include/linux/sched/user.h
@@ -4,6 +4,7 @@
#include <linux/uidgid.h>
#include <linux/atomic.h>
+#include <linux/refcount.h>
#include <linux/ratelimit.h>
struct key;
@@ -12,7 +13,7 @@ struct key;
* Some day this will be a full-fledged user tracking system..
*/
struct user_struct {
- atomic_t __count; /* reference count */
+ refcount_t __count; /* reference count */
atomic_t processes; /* How many processes does this user have? */
atomic_t sigpending; /* How many pending signals does this user have? */
#ifdef CONFIG_FANOTIFY
@@ -59,7 +60,7 @@ extern struct user_struct root_user;
extern struct user_struct * alloc_uid(kuid_t);
static inline struct user_struct *get_uid(struct user_struct *u)
{
- atomic_inc(&u->__count);
+ refcount_inc(&u->__count);
return u;
}
extern void free_uid(struct user_struct *);
diff -puN kernel/user.c~userns-use-refcount_t-for-reference-counting-instead-atomic_t kernel/user.c
--- a/kernel/user.c~userns-use-refcount_t-for-reference-counting-instead-atomic_t
+++ a/kernel/user.c
@@ -96,7 +96,7 @@ static DEFINE_SPINLOCK(uidhash_lock);
/* root_user.__count is 1, for init task cred */
struct user_struct root_user = {
- .__count = ATOMIC_INIT(1),
+ .__count = REFCOUNT_INIT(1),
.processes = ATOMIC_INIT(1),
.sigpending = ATOMIC_INIT(0),
.locked_shm = 0,
@@ -123,7 +123,7 @@ static struct user_struct *uid_hash_find
hlist_for_each_entry(user, hashent, uidhash_node) {
if (uid_eq(user->uid, uid)) {
- atomic_inc(&user->__count);
+ refcount_inc(&user->__count);
return user;
}
}
@@ -170,7 +170,7 @@ void free_uid(struct user_struct *up)
return;
local_irq_save(flags);
- if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
+ if (refcount_dec_and_lock(&up->__count, &uidhash_lock))
free_user(up, flags);
else
local_irq_restore(flags);
@@ -191,7 +191,7 @@ struct user_struct *alloc_uid(kuid_t uid
goto out_unlock;
new->uid = uid;
- atomic_set(&new->__count, 1);
+ refcount_set(&new->__count, 1);
ratelimit_state_init(&new->ratelimit, HZ, 100);
ratelimit_set_flags(&new->ratelimit, RATELIMIT_MSG_ON_RELEASE);
_
Patches currently in -mm which might be from bigeasy@xxxxxxxxxxxxx are
ntfs-dont-disable-interrupts-during-kmap_atomic.patch
mm-workingset-remove-local_irq_disable-from-count_shadow_nodes.patch
mm-workingset-make-shadow_lru_isolate-use-locking-suffix.patch
bdi-use-refcount_t-for-reference-counting-instead-atomic_t.patch
userns-use-refcount_t-for-reference-counting-instead-atomic_t.patch
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