From 97d0fb239c041f5f99655af74812c3ab75cc4346 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 3 Dec 2018 11:30:30 +1100 Subject: [PATCH] cred: add get_cred_rcu() Sometimes we want to opportunistically get a ref to a cred in an rcu_read_lock protected section. get_task_cred() does this, and NFS does as similar thing with its own credential structures. To prepare for NFS converting to use 'struct cred' more uniformly, define get_cred_rcu(), and use it in get_task_cred(). Signed-off-by: NeilBrown Signed-off-by: Anna Schumaker --- include/linux/cred.h | 11 +++++++++++ kernel/cred.c | 2 +- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/include/linux/cred.h b/include/linux/cred.h index f1085767e1b3..48979fcb95cf 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -252,6 +252,17 @@ static inline const struct cred *get_cred(const struct cred *cred) return get_new_cred(nonconst_cred); } +static inline const struct cred *get_cred_rcu(const struct cred *cred) +{ + struct cred *nonconst_cred = (struct cred *) cred; + if (!cred) + return NULL; + if (!atomic_inc_not_zero(&nonconst_cred->usage)) + return NULL; + validate_creds(cred); + return cred; +} + /** * put_cred - Release a reference to a set of credentials * @cred: The credentials to release diff --git a/kernel/cred.c b/kernel/cred.c index 0b3ac72bd717..ba60162249e8 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -195,7 +195,7 @@ const struct cred *get_task_cred(struct task_struct *task) do { cred = __task_cred((task)); BUG_ON(!cred); - } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage)); + } while (!get_cred_rcu(cred)); rcu_read_unlock(); return cred;