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Message-Id: <20231027063713.1018624-1-singhabhinav9051571833@gmail.com>
Date: Fri, 27 Oct 2023 12:07:13 +0530
From: Abhinav Singh <singhabhinav9051571833@...il.com>
To: akpm@...ux-foundation.org, brauner@...nel.org, surenb@...gle.com,
mst@...hat.com, michael.christie@...cle.com,
mathieu.desnoyers@...icios.com, mjguzik@...il.com,
npiggin@...il.com, shakeelb@...gle.com, peterz@...radead.org
Cc: linux-kernel@...r.kernel.org,
linux-kernel-mentees@...ts.linuxfoundation.org,
Abhinav Singh <singhabhinav9051571833@...il.com>
Subject: [PATCH v3] Fixing directly deferencing a __rcu pointer warning
This patch fixes the warning about directly dereferencing a pointer
tagged with __rcu annotation.
Dereferencing the pointers tagged with __rcu directly should
always be avoided according to the docs. There is a rcu helper
functions rcu_dereference(...) to use when dereferencing a __rcu
pointer. This functions returns the non __rcu tagged pointer which
can be dereferenced just like a normal pointers.
Signed-off-by: Abhinav Singh <singhabhinav9051571833@...il.com>
---
kernel/fork.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/fork.c b/kernel/fork.c
index 10917c3e1f03..e78649974669 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2369,7 +2369,7 @@ __latent_entropy struct task_struct *copy_process(
retval = -EAGAIN;
if (is_rlimit_overlimit(task_ucounts(p), UCOUNT_RLIMIT_NPROC, rlimit(RLIMIT_NPROC))) {
- if (p->real_cred->user != INIT_USER &&
+ if (rcu_dereference(p->real_cred)->user != INIT_USER &&
!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
goto bad_fork_cleanup_count;
}
@@ -2690,9 +2690,9 @@ __latent_entropy struct task_struct *copy_process(
* tasklist_lock with adding child to the process tree
* for propagate_has_child_subreaper optimization.
*/
- p->signal->has_child_subreaper = p->real_parent->signal->has_child_subreaper ||
- p->real_parent->signal->is_child_subreaper;
- list_add_tail(&p->sibling, &p->real_parent->children);
+ p->signal->has_child_subreaper = rcu_dereference(p->real_parent)->signal->has_child_subreaper ||
+ rcu_dereference(p->real_parent)->signal->is_child_subreaper;
+ list_add_tail(&p->sibling, &rcu_dereference(p->real_parent)->children);
list_add_tail_rcu(&p->tasks, &init_task.tasks);
attach_pid(p, PIDTYPE_TGID);
attach_pid(p, PIDTYPE_PGID);
--
2.39.2
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