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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Joe Perches <joe@perches.com>,
        Dan Carpenter <error27@gmail.com>,
        Julia Lawall <julia.lawall@lip6.fr>,
        Thomas Gleixner <tglx@linutronix.de>,
        Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.4 22/85] kernel/sys.c: avoid copying possible padding bytes in copy_to_user
Date:   Tue, 29 Sep 2020 12:59:49 +0200
Message-Id: <20200929105929.335177908@linuxfoundation.org>
In-Reply-To: <20200929105928.198942536@linuxfoundation.org>
References: <20200929105928.198942536@linuxfoundation.org>
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From: Joe Perches <joe@perches.com>

[ Upstream commit 5e1aada08cd19ea652b2d32a250501d09b02ff2e ]

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: Sasha Levin <sashal@kernel.org>
---
 kernel/sys.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index 1855f1bf113e4..e98664039cb23 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1183,11 +1183,13 @@ 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);
-- 
2.25.1