From d01fad2a8757f4e3b449a888b93a0ba9fda54daa Mon Sep 17 00:00:00 2001 From: Eduardo Otubo Date: Thu, 5 Mar 2020 13:49:51 +0100 Subject: [PATCH 6/6] seccomp: set the seccomp filter to all threads MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Message-id: <20200305134951.23851-1-otubo@redhat.com> Patchwork-id: 94161 O-Subject: [RHEL-7.9 qemu-kvm PATCH] seccomp: set the seccomp filter to all threads Bugzilla: 1618503 RH-Acked-by: Philippe Mathieu-Daudé RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Mohammed Gamal commit 70dfabeaa79ba4d7a3b699abe1a047c8012db114 Author: Marc-André Lureau Date: Wed Aug 22 19:02:50 2018 +0200 When using "-seccomp on", the seccomp policy is only applied to the main thread, the vcpu worker thread and other worker threads created after seccomp policy is applied; the seccomp policy is not applied to e.g. the RCU thread because it is created before the seccomp policy is applied and SECCOMP_FILTER_FLAG_TSYNC isn't used. This can be verified with for task in /proc/`pidof qemu`/task/*; do cat $task/status | grep Secc ; done Seccomp: 2 Seccomp: 0 Seccomp: 0 Seccomp: 2 Seccomp: 2 Seccomp: 2 Starting with libseccomp 2.2.0 and kernel >= 3.17, we can use seccomp_attr_set(ctx, > SCMP_FLTATR_CTL_TSYNC, 1) to update the policy on all threads. libseccomp requirement was bumped to 2.2.0 in previous patch. libseccomp should fail to set the filter if it can't honour SCMP_FLTATR_CTL_TSYNC (untested), and thus -sandbox will now fail on kernel < 3.17. Signed-off-by: Marc-André Lureau Acked-by: Eduardo Otubo Signed-off-by: Eduardo Otubo Signed-off-by: Miroslav Rezanina --- qemu-seccomp.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/qemu-seccomp.c b/qemu-seccomp.c index e947909..828083b 100644 --- a/qemu-seccomp.c +++ b/qemu-seccomp.c @@ -264,6 +264,11 @@ int seccomp_start(void) goto seccomp_return; } + rc = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_TSYNC, 1); + if (rc != 0) { + goto seccomp_return; + } + for (i = 0; i < ARRAY_SIZE(seccomp_whitelist); i++) { rc = seccomp_rule_add(ctx, SCMP_ACT_ALLOW, seccomp_whitelist[i].num, 0); if (rc < 0) { -- 1.8.3.1