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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 /init
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 'init')
-rw-r--r--init/initramfs.c2
-rw-r--r--init/main.c2
2 files changed, 3 insertions, 1 deletions
diff --git a/init/initramfs.c b/init/initramfs.c
index dc84cf756cea..18229cfe8906 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -15,6 +15,7 @@
#include <linux/mm.h>
#include <linux/namei.h>
#include <linux/init_syscalls.h>
+#include <linux/task_work.h>
#include <linux/umh.h>
static __initdata bool csum_present;
@@ -727,6 +728,7 @@ done:
initrd_end = 0;
flush_delayed_fput();
+ task_work_run();
}
static ASYNC_DOMAIN_EXCLUSIVE(initramfs_domain);
diff --git a/init/main.c b/init/main.c
index 02eb533018f6..0ee39cdcfcac 100644
--- a/init/main.c
+++ b/init/main.c
@@ -688,7 +688,7 @@ noinline void __ref rest_init(void)
* the init task will end up wanting to create kthreads, which, if
* we schedule it before we create kthreadd, will OOPS.
*/
- pid = kernel_thread(kernel_init, NULL, CLONE_FS);
+ pid = user_mode_thread(kernel_init, NULL, CLONE_FS);
/*
* Pin init on the boot CPU. Task migration is not properly working
* until sched_init_smp() has been run. It will set the allowed