From: Sargun Dhillon <sargun@sargun.me>
Date: Sun, 29 Dec 2019 06:24:50 +0000 (-0800)
Subject: seccomp: Check that seccomp_notif is zeroed out by the user
X-Git-Tag: v5.4.9~97
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f75e60d239087a582ca3d828fb475422d8046b79;p=platform%2Fkernel%2Flinux-rpi.git

seccomp: Check that seccomp_notif is zeroed out by the user

commit 2882d53c9c6f3b8311d225062522f03772cf0179 upstream.

This patch is a small change in enforcement of the uapi for
SECCOMP_IOCTL_NOTIF_RECV ioctl. Specifically, the datastructure which
is passed (seccomp_notif) must be zeroed out. Previously any of its
members could be set to nonsense values, and we would ignore it.

This ensures all fields are set to their zero value.

Signed-off-by: Sargun Dhillon <sargun@sargun.me>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Acked-by: Tycho Andersen <tycho@tycho.ws>
Link: https://lore.kernel.org/r/20191229062451.9467-2-sargun@sargun.me
Fixes: 6a21cc50f0c7 ("seccomp: add a return code to trap to userspace")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index dba52a7..614a557 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -1015,6 +1015,13 @@ static long seccomp_notify_recv(struct seccomp_filter *filter,
 	struct seccomp_notif unotif;
 	ssize_t ret;
 
+	/* Verify that we're not given garbage to keep struct extensible. */
+	ret = check_zeroed_user(buf, sizeof(unotif));
+	if (ret < 0)
+		return ret;
+	if (!ret)
+		return -EINVAL;
+
 	memset(&unotif, 0, sizeof(unotif));
 
 	ret = down_interruptible(&filter->notif->request);