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