Arnd Bergmann <arnd@xxxxxxxxxx> writes: > From: Arnd Bergmann <arnd@xxxxxxxx> > > There are no remaining callers of set_fs(), so CONFIG_SET_FS > can be removed globally, along with the thread_info field and > any references to it. > > This turns access_ok() into a cheaper check against TASK_SIZE_MAX. > > With CONFIG_SET_FS gone, so drop all remaining references to > set_fs()/get_fs(), mm_segment_t and uaccess_kernel(). For the bits I have looked at recently, and think I understand. Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> > > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > --- > fs/exec.c | 6 -- > kernel/exit.c | 14 ----- > kernel/kthread.c | 5 -- > > diff --git a/fs/exec.c b/fs/exec.c > index 79f2c9483302..bc68a0c089ac 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1303,12 +1303,6 @@ int begin_new_exec(struct linux_binprm * bprm) > if (retval) > goto out_unlock; > > - /* > - * Ensure that the uaccess routines can actually operate on userspace > - * pointers: > - */ > - force_uaccess_begin(); > - > if (me->flags & PF_KTHREAD) > free_kthread_struct(me); > me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD | > diff --git a/kernel/exit.c b/kernel/exit.c > index b00a25bb4ab9..0884a75bc2f8 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -737,20 +737,6 @@ void __noreturn do_exit(long code) > > WARN_ON(blk_needs_flush_plug(tsk)); > > - /* > - * If do_dead is called because this processes oopsed, it's possible > - * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before > - * continuing. Amongst other possible reasons, this is to prevent > - * mm_release()->clear_child_tid() from writing to a user-controlled > - * kernel address. > - * > - * On uptodate architectures force_uaccess_begin is a noop. On > - * architectures that still have set_fs/get_fs in addition to handling > - * oopses handles kernel threads that run as set_fs(KERNEL_DS) by > - * default. > - */ > - force_uaccess_begin(); > - > kcov_task_exit(tsk); > > coredump_task_exit(tsk); > diff --git a/kernel/kthread.c b/kernel/kthread.c > index 38c6dd822da8..16c2275d4b50 100644 > --- a/kernel/kthread.c > +++ b/kernel/kthread.c > @@ -55,7 +55,6 @@ struct kthread { > int result; > int (*threadfn)(void *); > void *data; > - mm_segment_t oldfs; > struct completion parked; > struct completion exited; > #ifdef CONFIG_BLK_CGROUP > @@ -1441,8 +1440,6 @@ void kthread_use_mm(struct mm_struct *mm) > mmdrop(active_mm); > else > smp_mb(); > - > - to_kthread(tsk)->oldfs = force_uaccess_begin(); > } > EXPORT_SYMBOL_GPL(kthread_use_mm); > > @@ -1457,8 +1454,6 @@ void kthread_unuse_mm(struct mm_struct *mm) > WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD)); > WARN_ON_ONCE(!tsk->mm); > > - force_uaccess_end(to_kthread(tsk)->oldfs); > - > task_lock(tsk); > /* > * When a kthread stops operating on an address space, the loop