From: "Eric W. Biederman" ebiederm@xmission.com
mainline inclusion from mainline-5.4-rc1 commit 3fbd7ee285b2bbc6eebd15a3c8786d9776a402a8 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I3UKOW CVE: NA
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Add a count of the number of RCU users (currently 1) of the task struct so that we can later add the scheduler case and get rid of the very subtle task_rcu_dereference(), and just use rcu_dereference().
As suggested by Oleg have the count overlap rcu_head so that no additional space in task_struct is required.
Inspired-by: Linus Torvalds torvalds@linux-foundation.org Inspired-by: Oleg Nesterov oleg@redhat.com Signed-off-by: Eric W. Biederman ebiederm@xmission.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: Chris Metcalf cmetcalf@ezchip.com Cc: Christoph Lameter cl@linux.com Cc: Davidlohr Bueso dave@stgolabs.net Cc: Kirill Tkhai tkhai@yandex.ru Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Mike Galbraith efault@gmx.de Cc: Paul E. McKenney paulmck@kernel.org Cc: Peter Zijlstra peterz@infradead.org Cc: Russell King - ARM Linux admin linux@armlinux.org.uk Cc: Thomas Gleixner tglx@linutronix.de Link: https://lkml.kernel.org/r/87woebdplt.fsf_-_@x220.int.ebiederm.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Li Hua hucool.lihua@huawei.com Signed-off-by: Zheng Zucheng zhengzucheng@huawei.com
Conflicts: kernel/fork.c Reviewed-by: Xie XiuQi xiexiuqi@huawei.com
Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- include/linux/sched.h | 5 ++++- include/linux/sched/task.h | 1 + kernel/exit.c | 7 ++++++- kernel/fork.c | 7 +++---- 4 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h index 8a09c0c018ec8..d4bd8429faa14 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1081,7 +1081,10 @@ struct task_struct {
struct tlbflush_unmap_batch tlb_ubc;
- struct rcu_head rcu; + union { + refcount_t rcu_users; + struct rcu_head rcu; + };
/* Cache last used pipe for splice(): */ struct pipe_inode_info *splice_pipe; diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index 5046980ecb0f8..b9b89a896714a 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -100,6 +100,7 @@ static inline void put_task_struct(struct task_struct *t) }
struct task_struct *task_rcu_dereference(struct task_struct **ptask); +void put_task_struct_rcu_user(struct task_struct *task);
#ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT extern int arch_task_struct_size __read_mostly; diff --git a/kernel/exit.c b/kernel/exit.c index 62cf0982d94b1..c52897b1877f3 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -172,6 +172,11 @@ static void delayed_put_task_struct(struct rcu_head *rhp) put_task_struct(tsk); }
+void put_task_struct_rcu_user(struct task_struct *task) +{ + if (refcount_dec_and_test(&task->rcu_users)) + call_rcu(&task->rcu, delayed_put_task_struct); +}
void release_task(struct task_struct *p) { @@ -212,7 +217,7 @@ void release_task(struct task_struct *p)
write_unlock_irq(&tasklist_lock); release_thread(p); - call_rcu(&p->rcu, delayed_put_task_struct); + put_task_struct_rcu_user(p);
p = leader; if (unlikely(zap_leader)) diff --git a/kernel/fork.c b/kernel/fork.c index 403b8a3315979..20df40eef876e 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -895,10 +895,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) tsk->stack_canary = get_random_canary(); #endif
- /* - * One for us, one for whoever does the "release_task()" (usually - * parent) - */ + /* One for the user space visible state that goes away when reaped. */ + refcount_set(&tsk->rcu_users, 1); + /* One for the rcu users, and one for the scheduler */ atomic_set(&tsk->usage, 2); #ifdef CONFIG_BLK_DEV_IO_TRACE tsk->btrace_seq = 0;