From: Jinliang Zheng <alexjlzheng@tencent.com> stable inclusion from stable-v6.6.128 commit 0e64bd46a04a4fd61279aca9f53a664e9e5f7e7e category: bugfix bugzilla: AR.SR.IR20250327002298.006.012 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 76149d53502cf17ef3ae454ff384551236fba867 ] When reading /proc/[pid]/stat, do_task_stat() accesses task->real_parent without proper RCU protection, which leads to: cpu 0 cpu 1 ----- ----- do_task_stat var = task->real_parent release_task call_rcu(delayed_put_task_struct) task_tgid_nr_ns(var) rcu_read_lock <--- Too late to protect task->real_parent! task_pid_ptr <--- UAF! rcu_read_unlock This patch uses task_ppid_nr_ns() instead of task_tgid_nr_ns() to add proper RCU protection for accessing task->real_parent. Link: https://lkml.kernel.org/r/20260128083007.3173016-1-alexjlzheng@tencent.com Fixes: 06fffb1267c9 ("do_task_stat: don't take rcu_read_lock()") Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: David Hildenbrand <david@kernel.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Mateusz Guzik <mjguzik@gmail.com> Cc: ruippan <ruippan@tencent.com> Cc: Usama Arif <usamaarif642@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Chen Jinghuang <chenjinghuang2@huawei.com> --- fs/proc/array.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/proc/array.c b/fs/proc/array.c index 6a4b0a850dce..288f19956e04 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -544,7 +544,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, } sid = task_session_nr_ns(task, ns); - ppid = task_tgid_nr_ns(task->real_parent, ns); + ppid = task_ppid_nr_ns(task, ns); pgid = task_pgrp_nr_ns(task, ns); unlock_task_sighand(task, &flags); -- 2.34.1