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seccomp: use SIGSYS signal instead of killing the thread

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The seccomp action SCMP_ACT_KILL results in immediate termination of
the thread that made the bad system call. However, qemu being
multi-threaded, it keeps running. There is no easy way for parent
process / management layer (libvirt) to know about that situation.

Instead, the default SIGSYS handler when invoked with SCMP_ACT_TRAP
will terminate the program and core dump.

This may not be the most secure solution, but probably better than
just killing the offending thread. SCMP_ACT_KILL_PROCESS has been
added in Linux 4.14 to improve the situation, which I propose to use
by default if available in the next patch.

Related to:
https://bugzilla.redhat.com/show_bug.cgi?id=1594456

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Eduardo Otubo <otubo@redhat.com>
This commit is contained in:
Marc-André Lureau 2018-08-22 19:02:47 +02:00 committed by Eduardo Otubo
parent 3392fbee4e
commit 6f2231e9b0
1 changed files with 1 additions and 1 deletions
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qemu-seccomp.c
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@ -125,7 +125,7 @@ static int seccomp_start(uint32_t seccomp_opts)
continue;
}
rc = seccomp_rule_add_array(ctx, SCMP_ACT_KILL, blacklist[i].num,
rc = seccomp_rule_add_array(ctx, SCMP_ACT_TRAP, blacklist[i].num,
blacklist[i].narg, blacklist[i].arg_cmp);
if (rc < 0) {
goto seccomp_return;