From: Christoph Hellwig <hch@lst.de>
Date: Wed, 12 Aug 2020 01:33:50 +0000 (-0700)
Subject: exec: use force_uaccess_begin during exec and exit
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=fe81417596fa8b6577fedb7e206ff3e4c7015c13;p=linux.git

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>
---

diff --git a/fs/exec.c b/fs/exec.c
index 3698252719a33..29ef78ae9f502 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 e731c414e024a..c2d2961576f2a 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",