From a10f52a7565c549612c92b8e736a6698a53db330 Mon Sep 17 00:00:00 2001 From: Simon McVittie Date: Wed, 1 Sep 2021 11:59:00 +0100 Subject: [PATCH] run: Block clone3() in sandbox clone3() can be used to implement clone() with CLONE_NEWUSER, allowing a sandboxed process to get CAP_SYS_ADMIN in a new namespace and manipulate its root directory. We need to block this so that AF_UNIX-based socket servers (X11, Wayland, etc.) can rely on /proc/PID/root/.flatpak-info existing for all Flatpak-sandboxed apps. Partially fixes GHSA-67h7-w3jq-vh4q. Thanks: an anonymous reporter Signed-off-by: Simon McVittie Conflict:NA Reference:https://github.com/flatpak/flatpak/commit/a10f52a7565c549612c92b8e736a6698a53db330 --- common/flatpak-run.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/common/flatpak-run.c b/common/flatpak-run.c index 5cf6d2e..dad0cfe 100644 --- a/common/flatpak-run.c +++ b/common/flatpak-run.c @@ -2832,6 +2832,12 @@ setup_seccomp (FlatpakBwrap *bwrap, /* Don't allow faking input to the controlling tty (CVE-2017-5226) */ {SCMP_SYS (ioctl), EPERM, &SCMP_A1 (SCMP_CMP_MASKED_EQ, 0xFFFFFFFFu, (int) TIOCSTI)}, + + /* seccomp can't look into clone3()'s struct clone_args to check whether + * the flags are OK, so we have no choice but to block clone3(). + * Return ENOSYS so user-space will fall back to clone(). + * (GHSA-67h7-w3jq-vh4q; see also https://github.com/moby/moby/commit/9f6b562d) */ + {SCMP_SYS (clone3), ENOSYS}, }; struct -- 2.27.0