linux-kernel - drivers/s390/char/keyboard.c kernel stack infoleak

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Date:   Thu, 3 Aug 2017 21:59:31 +0800 (CST)
From:   sohu0106 <sohu0106@....com>
To:     schwidefsky@...ibm.com, heiko.carstens@...ibm.com
Cc:     linux-s390@...r.kernel.org, torvalds@...ux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: drivers/s390/char/keyboard.c kernel stack infoleak


The stack object "kbdiacr" has a total size of 4 bytes. Its last 1 bytes are padding bytes after "result" which are not initialized and leaked to userland via "copy_to_user".


diff --git a/keyboard.c b/keyboard.c
index ba0e4f9..76a6d35 100644
--- a/keyboard.c
+++ b/keyboard.c
@@ -480,6 +480,8 @@ int kbd_ioctl(struct kbd_data *kbd, unsigned int cmd, unsigned long arg)
                struct kbdiacr diacr;
                int i;
 
+               memset( &diacr, 0, sizeof(struct kbdiacr) );
+
                if (put_user(kbd->accent_table_size, &a->kb_cnt))
                        return -EFAULT;
                for (i = 0; i < kbd->accent_table_size; i++) {