[RFC PATCH v3 1/8] Use refcount_t for ucounts reference counting

Alexey Gladkov
2021-01-15T14:59:17Z

Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
---
include/linux/user_namespace.h | 2 +-
kernel/ucount.c | 20 +++++++-------------
2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index 64cf8ebdc4ec..f84fc2d9ce20 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -92,7 +92,7 @@ struct ucounts {
struct hlist_node node;
struct user_namespace *ns;
kuid_t uid;
- int count;
+ refcount_t count;
atomic_t ucount[UCOUNT_COUNTS];
};

diff --git a/kernel/ucount.c b/kernel/ucount.c
index 11b1596e2542..82acd2226460 100644
--- a/kernel/ucount.c
+++ b/kernel/ucount.c
@@ -141,7 +141,8 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)

new->ns = ns;
new->uid = uid;
- new->count = 0;
+
+ refcount_set(&new->count, 0);

spin_lock_irq(&ucounts_lock);
ucounts = find_ucounts(ns, uid, hashent);
@@ -152,10 +153,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
ucounts = new;
}
}
- if (ucounts->count == INT_MAX)
- ucounts = NULL;
- else
- ucounts->count += 1;
+ refcount_inc(&ucounts->count);
spin_unlock_irq(&ucounts_lock);
return ucounts;
}
@@ -164,15 +162,11 @@ static void put_ucounts(struct ucounts *ucounts)
{
unsigned long flags;

- spin_lock_irqsave(&ucounts_lock, flags);
- ucounts->count -= 1;
- if (!ucounts->count)
+ if (refcount_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, &flags)) {
hlist_del_init(&ucounts->node);
- else
- ucounts = NULL;
- spin_unlock_irqrestore(&ucounts_lock, flags);
-
- kfree(ucounts);
+ spin_unlock_irqrestore(&ucounts_lock, flags);
+ kfree(ucounts);
+ }
}

static inline bool atomic_inc_below(atomic_t *v, int u)
--
2.29.2