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authorLinus Torvalds <torvalds@linux-foundation.org>2022-06-03 16:03:05 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-06-03 16:03:05 -0700
commit1ec6574a3c0a22c130c08e8c36c825cb87d68f8e (patch)
tree1f064c4a4965b9b0dd213456649b23e066d54bea /arch/um
parent1888e9b4bb78c88514b24ecafa9e4e4faf761747 (diff)
parentb3f9916d81e8ffb21cbe7abccf63f86a5a1d598a (diff)
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 40966e316f86 ("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 343f4c49f243 ("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
Diffstat (limited to 'arch/um')
-rw-r--r--arch/um/kernel/process.c15
1 files changed, 8 insertions, 7 deletions
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 80504680be08..181cc9aafb25 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -154,16 +154,17 @@ void fork_handler(void)
userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
}
-int copy_thread(unsigned long clone_flags, unsigned long sp,
- unsigned long arg, struct task_struct * p, unsigned long tls)
+int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
{
+ unsigned long clone_flags = args->flags;
+ unsigned long sp = args->stack;
+ unsigned long tls = args->tls;
void (*handler)(void);
- int kthread = current->flags & (PF_KTHREAD | PF_IO_WORKER);
int ret = 0;
p->thread = (struct thread_struct) INIT_THREAD;
- if (!kthread) {
+ if (!args->fn) {
memcpy(&p->thread.regs.regs, current_pt_regs(),
sizeof(p->thread.regs.regs));
PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
@@ -175,14 +176,14 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
arch_copy_thread(&current->thread.arch, &p->thread.arch);
} else {
get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
- p->thread.request.u.thread.proc = (int (*)(void *))sp;
- p->thread.request.u.thread.arg = (void *)arg;
+ p->thread.request.u.thread.proc = args->fn;
+ p->thread.request.u.thread.arg = args->fn_arg;
handler = new_thread_handler;
}
new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
- if (!kthread) {
+ if (!args->fn) {
clear_flushed_tls(p);
/*