[068/165] exec: use force_uaccess_begin during exec and exit

Commit Message

Andrew Morton Aug. 12, 2020, 1:33 a.m. UTC

From: Christoph Hellwig <[e-mail]>
Subject: exec: use force_uaccess_begin during exec and exit

Both exec and exit want to ensure that the uaccess routines actually do
access user pointers.  Use the newly added force_uaccess_begin helper
instead of an open coded set_fs for that to prepare for kernel builds
where set_fs() does not exist.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Christoph Hellwig <[e-mail]>
Acked-by: Linus Torvalds <[e-mail]>
Cc: Nick Hu <[e-mail]>
Cc: Greentime Hu <[e-mail]>
Cc: Vincent Chen <[e-mail]>
Cc: Paul Walmsley <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 fs/exec.c     |    7 ++++++-
 kernel/exit.c |    2 +-
 2 files changed, 7 insertions(+), 2 deletions(-)

Patch

--- a/fs/exec.c~exec-use-force_uaccess_begin-during-exec-and-exit
+++ a/fs/exec.c
@@ -1402,7 +1402,12 @@  int begin_new_exec(struct linux_binprm *
 	if (retval)
 		goto out_unlock;
 
-	set_fs(USER_DS);
+	/*
+	 * Ensure that the uaccess routines can actually operate on userspace
+	 * pointers:
+	 */
+	force_uaccess_begin();
+
 	me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
 					PF_NOFREEZE | PF_NO_SETAFFINITY);
 	flush_thread();
--- a/kernel/exit.c~exec-use-force_uaccess_begin-during-exec-and-exit
+++ a/kernel/exit.c
@@ -732,7 +732,7 @@  void __noreturn do_exit(long code)
 	 * mm_release()->clear_child_tid() from writing to a user-controlled
 	 * kernel address.
 	 */
-	set_fs(USER_DS);
+	force_uaccess_begin();
 
 	if (unlikely(in_atomic())) {
 		pr_info("note: %s[%d] exited with preempt_count %d\n",