From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 3 Jun 2022 23:03:05 +0000 (-0700)
Subject: Merge tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel... 
X-Git-Tag: baikal/mips/sdk6.1~5569
X-Git-Url: https://git.baikalelectronics.ru/?a=commitdiff_plain;h=f73e145f46a948adb297640c7f9ca73267b09c25;p=kernel.git

Merge tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull kthread updates from Eric Biederman:
 "This updates init and user mode helper tasks to be ordinary user mode
  tasks.

  Commit 169a5179aab6 ("kthread: Ensure struct kthread is present for
  all kthreads") caused init and the user mode helper threads that call
  kernel_execve to have struct kthread allocated for them. This struct
  kthread going away during execve in turned made a use after free of
  struct kthread possible.

  Here, commit 14549687236b ("kthread: Don't allocate kthread_struct for
  init and umh") is enough to fix the use after free and is simple
  enough to be backportable.

  The rest of the changes pass struct kernel_clone_args to clean things
  up and cause the code to make sense.

  In making init and the user mode helpers tasks purely user mode tasks
  I ran into two complications. The function task_tick_numa was
  detecting tasks without an mm by testing for the presence of
  PF_KTHREAD. The initramfs code in populate_initrd_image was using
  flush_delayed_fput to ensuere the closing of all it's file descriptors
  was complete, and flush_delayed_fput does not work in a userspace
  thread.

  I have looked and looked and more complications and in my code review
  I have not found any, and neither has anyone else with the code
  sitting in linux-next"

* tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  sched: Update task_tick_numa to ignore tasks without an mm
  fork: Stop allowing kthreads to call execve
  fork: Explicitly set PF_KTHREAD
  init: Deal with the init process being a user mode process
  fork: Generalize PF_IO_WORKER handling
  fork: Explicity test for idle tasks in copy_thread
  fork: Pass struct kernel_clone_args into copy_thread
  kthread: Don't allocate kthread_struct for init and umh
---

f73e145f46a948adb297640c7f9ca73267b09c25
diff --cc arch/x86/kernel/process.c
index 58fb48d3004fe,d20eaad52a859..9b2772b7e1f39
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@@ -193,10 -193,14 +195,10 @@@ int copy_thread(struct task_struct *p, 
  	if (sp)
  		childregs->sp = sp;
  
- 	if (unlikely(p->flags & PF_IO_WORKER)) {
 -#ifdef CONFIG_X86_32
 -	task_user_gs(p) = get_user_gs(current_pt_regs());
 -#endif
 -
+ 	if (unlikely(args->fn)) {
  		/*
- 		 * An IO thread is a user space thread, but it doesn't
- 		 * return to ret_after_fork().
+ 		 * A user space thread, but it doesn't return to
+ 		 * ret_after_fork().
  		 *
  		 * In order to indicate that to tools like gdb,
  		 * we reset the stack and instruction pointers.
diff --cc init/initramfs.c
index dc84cf756cea1,41e7857d510d6..18229cfe8906b
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@@ -15,13 -15,11 +15,14 @@@
  #include <linux/mm.h>
  #include <linux/namei.h>
  #include <linux/init_syscalls.h>
+ #include <linux/task_work.h>
  #include <linux/umh.h>
  
 -static ssize_t __init xwrite(struct file *file, const char *p, size_t count,
 -		loff_t *pos)
 +static __initdata bool csum_present;
 +static __initdata u32 io_csum;
 +
 +static ssize_t __init xwrite(struct file *file, const unsigned char *p,
 +		size_t count, loff_t *pos)
  {
  	ssize_t out = 0;