procfs: fix missing RCU protection when reading real_parent in do_task_stat()

Description

In the Linux kernel, the following vulnerability has been resolved: procfs: fix missing RCU protection when reading real_parent in do_task_stat() 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.

Affected Products

Also Affects

Downstream vendors/products affected by this vulnerability

References

• https://git.kernel.org/stable/c/fefa0fcd78be465b7ad4c497fa6ec90d64194c04
• https://git.kernel.org/stable/c/c93a33f28f915d446eea6fb3f0e1def0b3af1982
• https://git.kernel.org/stable/c/1c8dc5b5517546c68ffae40b948336122bb61306
• https://git.kernel.org/stable/c/0e64bd46a04a4fd61279aca9f53a664e9e5f7e7e
• https://git.kernel.org/stable/c/73ec7c96601d61d52310c659145bb06d933a0fa6
• https://git.kernel.org/stable/c/4f9ae386861e280b7631ca252f798d25575627ee
• https://git.kernel.org/stable/c/dd8b13cb4ff1a4545a214ed897fdf2bc341155b6
• https://git.kernel.org/stable/c/76149d53502cf17ef3ae454ff384551236fba867

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