2016-05-26 22:42:29 +02:00
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/***
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This file is part of systemd.
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Copyright 2016 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <linux/netlink.h>
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#include <sys/capability.h>
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#include <sys/types.h>
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#ifdef HAVE_SECCOMP
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#include <seccomp.h>
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#endif
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#include "log.h"
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#ifdef HAVE_SECCOMP
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#include "seccomp-util.h"
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#endif
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#include "nspawn-seccomp.h"
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#ifdef HAVE_SECCOMP
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static int seccomp_add_default_syscall_filter(scmp_filter_ctx ctx,
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uint64_t cap_list_retain) {
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unsigned i;
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int r;
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static const struct {
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uint64_t capability;
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int syscall_num;
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} blacklist[] = {
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2016-06-10 18:04:02 +02:00
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{ 0, SCMP_SYS(_sysctl) }, /* obsolete syscall */
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{ 0, SCMP_SYS(add_key) }, /* keyring is not namespaced */
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{ 0, SCMP_SYS(afs_syscall) }, /* obsolete syscall */
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{ 0, SCMP_SYS(bdflush) },
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#ifdef __NR_bpf
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{ 0, SCMP_SYS(bpf) },
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#endif
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{ 0, SCMP_SYS(break) }, /* obsolete syscall */
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{ 0, SCMP_SYS(create_module) }, /* obsolete syscall */
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{ 0, SCMP_SYS(ftime) }, /* obsolete syscall */
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{ 0, SCMP_SYS(get_kernel_syms) }, /* obsolete syscall */
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{ 0, SCMP_SYS(getpmsg) }, /* obsolete syscall */
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{ 0, SCMP_SYS(gtty) }, /* obsolete syscall */
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#ifdef __NR_kexec_file_load
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{ 0, SCMP_SYS(kexec_file_load) },
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#endif
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{ 0, SCMP_SYS(kexec_load) },
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{ 0, SCMP_SYS(keyctl) }, /* keyring is not namespaced */
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{ 0, SCMP_SYS(lock) }, /* obsolete syscall */
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{ 0, SCMP_SYS(lookup_dcookie) },
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{ 0, SCMP_SYS(mpx) }, /* obsolete syscall */
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{ 0, SCMP_SYS(nfsservctl) }, /* obsolete syscall */
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{ 0, SCMP_SYS(open_by_handle_at) },
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{ 0, SCMP_SYS(perf_event_open) },
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{ 0, SCMP_SYS(prof) }, /* obsolete syscall */
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{ 0, SCMP_SYS(profil) }, /* obsolete syscall */
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{ 0, SCMP_SYS(putpmsg) }, /* obsolete syscall */
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{ 0, SCMP_SYS(query_module) }, /* obsolete syscall */
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{ 0, SCMP_SYS(quotactl) },
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{ 0, SCMP_SYS(request_key) }, /* keyring is not namespaced */
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{ 0, SCMP_SYS(security) }, /* obsolete syscall */
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{ 0, SCMP_SYS(sgetmask) }, /* obsolete syscall */
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{ 0, SCMP_SYS(ssetmask) }, /* obsolete syscall */
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{ 0, SCMP_SYS(stty) }, /* obsolete syscall */
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{ 0, SCMP_SYS(swapoff) },
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{ 0, SCMP_SYS(swapon) },
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{ 0, SCMP_SYS(sysfs) }, /* obsolete syscall */
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{ 0, SCMP_SYS(tuxcall) }, /* obsolete syscall */
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{ 0, SCMP_SYS(ulimit) }, /* obsolete syscall */
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{ 0, SCMP_SYS(uselib) }, /* obsolete syscall */
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{ 0, SCMP_SYS(ustat) }, /* obsolete syscall */
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{ 0, SCMP_SYS(vserver) }, /* obsolete syscall */
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{ CAP_SYSLOG, SCMP_SYS(syslog) },
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{ CAP_SYS_MODULE, SCMP_SYS(delete_module) },
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{ CAP_SYS_MODULE, SCMP_SYS(finit_module) },
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{ CAP_SYS_MODULE, SCMP_SYS(init_module) },
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{ CAP_SYS_PACCT, SCMP_SYS(acct) },
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{ CAP_SYS_PTRACE, SCMP_SYS(process_vm_readv) },
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{ CAP_SYS_PTRACE, SCMP_SYS(process_vm_writev) },
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{ CAP_SYS_PTRACE, SCMP_SYS(ptrace) },
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{ CAP_SYS_RAWIO, SCMP_SYS(ioperm) },
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{ CAP_SYS_RAWIO, SCMP_SYS(iopl) },
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{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_iobase) },
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{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_read) },
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{ CAP_SYS_RAWIO, SCMP_SYS(pciconfig_write) },
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#ifdef __NR_s390_pci_mmio_read
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{ CAP_SYS_RAWIO, SCMP_SYS(s390_pci_mmio_read) },
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#endif
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#ifdef __NR_s390_pci_mmio_write
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{ CAP_SYS_RAWIO, SCMP_SYS(s390_pci_mmio_write) },
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#endif
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{ CAP_SYS_TIME, SCMP_SYS(adjtimex) },
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{ CAP_SYS_TIME, SCMP_SYS(clock_adjtime) },
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{ CAP_SYS_TIME, SCMP_SYS(clock_settime) },
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{ CAP_SYS_TIME, SCMP_SYS(settimeofday) },
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{ CAP_SYS_TIME, SCMP_SYS(stime) },
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2016-05-26 22:42:29 +02:00
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};
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for (i = 0; i < ELEMENTSOF(blacklist); i++) {
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2016-06-10 18:04:02 +02:00
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if (blacklist[i].capability != 0 && (cap_list_retain & (1ULL << blacklist[i].capability)))
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2016-05-26 22:42:29 +02:00
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continue;
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r = seccomp_rule_add(ctx, SCMP_ACT_ERRNO(EPERM), blacklist[i].syscall_num, 0);
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if (r == -EFAULT)
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continue; /* unknown syscall */
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2016-07-23 02:27:45 +02:00
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if (r < 0)
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return log_error_errno(r, "Failed to block syscall: %m");
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2016-05-26 22:42:29 +02:00
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}
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return 0;
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}
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int setup_seccomp(uint64_t cap_list_retain) {
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scmp_filter_ctx seccomp;
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int r;
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seccomp = seccomp_init(SCMP_ACT_ALLOW);
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if (!seccomp)
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return log_oom();
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r = seccomp_add_secondary_archs(seccomp);
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if (r < 0) {
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log_error_errno(r, "Failed to add secondary archs to seccomp filter: %m");
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goto finish;
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}
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r = seccomp_add_default_syscall_filter(seccomp, cap_list_retain);
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if (r < 0)
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goto finish;
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/*
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Audit is broken in containers, much of the userspace audit
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hookup will fail if running inside a container. We don't
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care and just turn off creation of audit sockets.
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This will make socket(AF_NETLINK, *, NETLINK_AUDIT) fail
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with EAFNOSUPPORT which audit userspace uses as indication
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that audit is disabled in the kernel.
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*/
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r = seccomp_rule_add(
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seccomp,
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SCMP_ACT_ERRNO(EAFNOSUPPORT),
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SCMP_SYS(socket),
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2,
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SCMP_A0(SCMP_CMP_EQ, AF_NETLINK),
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SCMP_A2(SCMP_CMP_EQ, NETLINK_AUDIT));
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if (r < 0) {
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log_error_errno(r, "Failed to add audit seccomp rule: %m");
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goto finish;
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}
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r = seccomp_attr_set(seccomp, SCMP_FLTATR_CTL_NNP, 0);
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if (r < 0) {
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log_error_errno(r, "Failed to unset NO_NEW_PRIVS: %m");
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goto finish;
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}
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r = seccomp_load(seccomp);
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if (r == -EINVAL) {
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log_debug_errno(r, "Kernel is probably not configured with CONFIG_SECCOMP. Disabling seccomp audit filter: %m");
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r = 0;
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goto finish;
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}
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if (r < 0) {
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log_error_errno(r, "Failed to install seccomp audit filter: %m");
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goto finish;
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}
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finish:
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seccomp_release(seccomp);
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return r;
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}
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#else
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int setup_seccomp(uint64_t cap_list_retain) {
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return 0;
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}
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#endif
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