4.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jann Horn jannh@google.com
commit 0a0b98734479aa5b3c671d5190e86273372cab95 upstream.
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 jannh@google.com Acked-by: Kees Cook keescook@chromium.org Acked-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/compat.c | 1 + 1 file changed, 1 insertion(+)
--- a/kernel/compat.c +++ b/kernel/compat.c @@ -34,6 +34,7 @@ int compat_get_timex(struct timex *txc, { struct compat_timex tx32;
+ memset(txc, 0, sizeof(struct timex)); if (copy_from_user(&tx32, utp, sizeof(struct compat_timex))) return -EFAULT;