kernel/sys.c: avoid copying possible padding bytes in copy_to_user

[ 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>

diff --git a/kernel/sys.c b/kernel/sys.c
index 157277c..546cdc9 100644 (file)
--- 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);