From: Leon Yu <chianglungyu@gmail.com>
Date: Tue, 6 Mar 2018 23:16:24 +0800
Subject: module: propagate error in modules_open()
Patch-mainline: v4.16-rc7
Git-commit: 3f553b308bb004eb730da8e00a28150c157c7724
References: bsc#1109837

otherwise kernel can oops later in seq_release() due to dereferencing null
file->private_data which is only set if seq_open() succeeds.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
IP: seq_release+0xc/0x30
Call Trace:
 close_pdeo+0x37/0xd0
 proc_reg_release+0x5d/0x60
 __fput+0x9d/0x1d0
 ____fput+0x9/0x10
 task_work_run+0x75/0x90
 do_exit+0x252/0xa00
 do_group_exit+0x36/0xb0
 SyS_exit_group+0xf/0x10

Fixes: 516fb7f2e73d ("/proc/module: use the same logic as /proc/kallsyms for address exposure")
Cc: Jessica Yu <jeyu@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org # 4.15+
Signed-off-by: Leon Yu <chianglungyu@gmail.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/module.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/module.c
+++ b/kernel/module.c
@@ -4195,7 +4195,7 @@ static int modules_open(struct inode *in
 		m->private = kallsyms_show_value() ? NULL : (void *)8ul;
 	}
 
-	return 0;
+	return err;
 }
 
 static const struct file_operations proc_modules_operations = {