[23/86] kernel/sys.c: avoid copying possible padding bytes in copy_to_user

Commit Message

Andrew Morton Dec. 5, 2019, 12:50 a.m. UTC

From: Joe Perches <[e-mail]>
Subject: 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.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Joe Perches <[e-mail]>
Cc: Dan Carpenter <[e-mail]>
Cc: Julia Lawall <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Kees Cook <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 kernel/sys.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

--- a/kernel/sys.c~kernel-sysc-avoid-copying-possible-padding-bytes-in-copy_to_user
+++ a/kernel/sys.c
@@ -1279,11 +1279,13 @@  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);