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
