From 0a0b98734479aa5b3c671d5190e86273372cab95 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Fri, 11 May 2018 02:19:01 +0200 Subject: [PATCH] compat: fix 4-byte infoleak via uninitialized struct field Commit 3a4d44b61625 ("ntp: Move adjtimex related compat syscalls to native counterparts") removed the memset() in compat_get_timex(). Since then, the compat adjtimex syscall can invoke do_adjtimex() with an uninitialized ->tai. If do_adjtimex() doesn't write to ->tai (e.g. because the arguments are invalid), compat_put_timex() then copies the uninitialized ->tai field to userspace. Fix it by adding the memset() back. Fixes: 3a4d44b61625 ("ntp: Move adjtimex related compat syscalls to native counterparts") Signed-off-by: Jann Horn Acked-by: Kees Cook Acked-by: Al Viro Signed-off-by: Linus Torvalds --- kernel/compat.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/compat.c b/kernel/compat.c index 6d21894806b4..92d8c98c0f57 100644 --- a/kernel/compat.c +++ b/kernel/compat.c @@ -34,6 +34,7 @@ int compat_get_timex(struct timex *txc, const struct compat_timex __user *utp) { struct compat_timex tx32; + memset(txc, 0, sizeof(struct timex)); if (copy_from_user(&tx32, utp, sizeof(struct compat_timex))) return -EFAULT; -- 2.30.2