From: Joe Perches <joe@perches.com>
Date: Wed, 4 Dec 2019 16:50:53 -0800
Subject: kernel/sys.c: avoid copying possible padding bytes in copy_to_user
Git-commit: 5e1aada08cd19ea652b2d32a250501d09b02ff2e
Patch-mainline: 5.5-rc1
References: git-fixes

Initialization is not guaranteed to zero padding bytes so use an
explicit memset instead to avoid leaking any kernel content in any
possible padding bytes.

Link: http://lkml.kernel.org/r/dfa331c00881d61c8ee51577a082d8bebd61805c.camel@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 kernel/sys.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1199,11 +1199,13 @@ SYSCALL_DEFINE1(uname, struct old_utsnam
 
 SYSCALL_DEFINE1(olduname, struct oldold_utsname __user *, name)
 {
-	struct oldold_utsname tmp = {};
+	struct oldold_utsname tmp;
 
 	if (!name)
 		return -EFAULT;
 
+	memset(&tmp, 0, sizeof(tmp));
+
 	down_read(&uts_sem);
 	memcpy(&tmp.sysname, &utsname()->sysname, __OLD_UTS_LEN);
 	memcpy(&tmp.nodename, &utsname()->nodename, __OLD_UTS_LEN);