From fe81417596fa8b6577fedb7e206ff3e4c7015c13 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Tue, 11 Aug 2020 18:33:50 -0700
Subject: [PATCH] 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.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Link: http://lkml.kernel.org/r/20200710135706.537715-7-hch@lst.de
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/exec.c | 7 ++++++-
kernel/exit.c | 2 +-
2 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index 3698252719a3..29ef78ae9f50 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1402,7 +1402,12 @@ int begin_new_exec(struct linux_binprm * bprm)
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();
diff --git a/kernel/exit.c b/kernel/exit.c
index e731c414e024..c2d2961576f2 100644
--- a/kernel/exit.c
+++ b/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",