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authorLinus Torvalds <torvalds@linux-foundation.org>2022-06-04 02:03:05 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2022-06-04 02:03:05 +0300
commit1ec6574a3c0a22c130c08e8c36c825cb87d68f8e (patch)
tree1f064c4a4965b9b0dd213456649b23e066d54bea /arch/arm64/kernel/process.c
parent1888e9b4bb78c88514b24ecafa9e4e4faf761747 (diff)
parentb3f9916d81e8ffb21cbe7abccf63f86a5a1d598a (diff)
downloadlinux-1ec6574a3c0a22c130c08e8c36c825cb87d68f8e.tar.xz
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/arm64/kernel/process.c')
-rw-r--r--arch/arm64/kernel/process.c12
1 files changed, 7 insertions, 5 deletions
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 2f42123e059f..92bcc1768f0b 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -343,9 +343,11 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
asmlinkage void ret_from_fork(void) asm("ret_from_fork");
-int copy_thread(unsigned long clone_flags, unsigned long stack_start,
- unsigned long stk_sz, 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 stack_start = args->stack;
+ unsigned long tls = args->tls;
struct pt_regs *childregs = task_pt_regs(p);
memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
@@ -361,7 +363,7 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
ptrauth_thread_init_kernel(p);
- if (likely(!(p->flags & (PF_KTHREAD | PF_IO_WORKER)))) {
+ if (likely(!args->fn)) {
*childregs = *current_pt_regs();
childregs->regs[0] = 0;
@@ -399,8 +401,8 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
memset(childregs, 0, sizeof(struct pt_regs));
childregs->pstate = PSR_MODE_EL1h | PSR_IL_BIT;
- p->thread.cpu_context.x19 = stack_start;
- p->thread.cpu_context.x20 = stk_sz;
+ p->thread.cpu_context.x19 = (unsigned long)args->fn;
+ p->thread.cpu_context.x20 = (unsigned long)args->fn_arg;
}
p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
p->thread.cpu_context.sp = (unsigned long)childregs;