6.1-stable review patch. If anyone has any objections, please let me know.
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From: Oleg Nesterov oleg@redhat.com
[ Upstream commit abdfd4948e45c51b19162cf8b3f5003f8f53c9b9 ]
task_pid_vnr(another_task) will crash if the caller was already reaped. The pid_alive(current) check can't really help, the parent/debugger can call release_task() right after this check.
This also means that even task_ppid_nr_ns(current, NULL) is not safe, pid_alive() only ensures that it is safe to dereference ->real_parent.
Change __task_pid_nr_ns() to ensure ns != NULL.
Originally-by: 高翔 gaoxiang17@xiaomi.com Link: https://lore.kernel.org/all/20250802022123.3536934-1-gxxa03070307@gmail.com/ Signed-off-by: Oleg Nesterov oleg@redhat.com Link: https://lore.kernel.org/20250810173604.GA19991@redhat.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/pid.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/pid.c b/kernel/pid.c index e1d0c9d952278..62a8349267de1 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -497,7 +497,8 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, rcu_read_lock(); if (!ns) ns = task_active_pid_ns(current); - nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns); + if (ns) + nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns); rcu_read_unlock();
return nr;