seccomp: Check that seccomp_notif is zeroed out by the user

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 <[email protected]> Reviewed-by: Christian Brauner <[email protected]> Reviewed-by: Aleksa Sarai <[email protected]> Acked-by: Tycho Andersen <[email protected]> Link: https://lore.kernel.org/r/[email protected] Fixes: 6a21cc5 ("seccomp: add a return code to trap to userspace") Cc: [email protected] Signed-off-by: Kees Cook <[email protected]>
niw · Jan 2, 2020 · 2882d53 · 2882d53
1 parent 88c13f8
commit 2882d53
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
@@ -1026,6 +1026,13 @@ 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);