linux-kernel - [PATCH] kernel: sys.c: Avoid copying possible padding bytes in copy_to

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Date:   Sat, 26 Oct 2019 12:46:08 -0700
From:   Joe Perches <joe@...ches.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Dan Carpenter <error27@...il.com>,
        Julia Lawall <julia.lawall@...6.fr>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] kernel: sys.c: Avoid copying possible padding bytes in
 copy_to_user

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.

Signed-off-by: Joe Perches <joe@...ches.com>
---
 kernel/sys.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index a611d1..3459a5 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1279,11 +1279,13 @@ SYSCALL_DEFINE1(uname, struct old_utsname __user *, name)
 
 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);