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virtiofsd: add seccomp whitelist 

Only allow system calls that are needed by virtiofsd.  All other system
calls cause SIGSYS to be directed at the thread and the process will
coredump.

Restricting system calls reduces the kernel attack surface and limits
what the process can do when compromised.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
with additional entries by:
Signed-off-by: Ganesh Maharaj Mahalingam <ganesh.mahalingam@intel.com>
Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: Misono Tomohiro <misono.tomohiro@jp.fujitsu.com>
Signed-off-by: piaojun <piaojun@huawei.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Eric Ren <renzhen@linux.alibaba.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2019-03-13 09:32:51 +00:00 committed by Dr. David Alan Gilbert
parent 8e1d4ef231
commit 4f8bde99c1
5 changed files with 174 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
Makefile
View File

@ -327,7 +327,7 @@ HELPERS-y += vhost-user-gpu$(EXESUF)
vhost-user-json-y += contrib/vhost-user-gpu/50-qemu-gpu.json
endif
ifdef CONFIG_LINUX
ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP),yy)
HELPERS-y += virtiofsd$(EXESUF)
vhost-user-json-y += tools/virtiofsd/50-qemu-virtiofsd.json
endif
@ -674,7 +674,8 @@ rdmacm-mux$(EXESUF): LIBS += "-libumad"
rdmacm-mux$(EXESUF): $(rdmacm-mux-obj-y) $(COMMON_LDADDS)
$(call LINK, $^)
ifdef CONFIG_LINUX # relies on Linux-specific syscalls
# relies on Linux-specific syscalls
ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP),yy)
virtiofsd$(EXESUF): $(virtiofsd-obj-y) libvhost-user.a $(COMMON_LDADDS)
$(call LINK, $^)
endif

5
tools/virtiofsd/Makefile.objs
View File

@ -5,5 +5,8 @@ virtiofsd-obj-y = buffer.o \
fuse_signals.o \
fuse_virtio.o \
helper.o \
passthrough_ll.o
passthrough_ll.o \
seccomp.o
seccomp.o-cflags := $(SECCOMP_CFLAGS)
seccomp.o-libs := $(SECCOMP_LIBS)

2
tools/virtiofsd/passthrough_ll.c
View File

@ -59,6 +59,7 @@
#include <unistd.h>
#include "passthrough_helpers.h"
#include "seccomp.h"
struct lo_map_elem {
union {
@ -2091,6 +2092,7 @@ static void setup_sandbox(struct lo_data *lo, struct fuse_session *se)
{
setup_namespaces(lo, se);
setup_mounts(lo->source);
setup_seccomp();
}
int main(int argc, char *argv[])

151
tools/virtiofsd/seccomp.c Normal file
View File

@ -0,0 +1,151 @@
/*
* Seccomp sandboxing for virtiofsd
*
* Copyright (C) 2019 Red Hat, Inc.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "qemu/osdep.h"
#include "seccomp.h"
#include "fuse_i.h"
#include "fuse_log.h"
#include <errno.h>
#include <glib.h>
#include <seccomp.h>
#include <stdlib.h>
/* Bodge for libseccomp 2.4.2 which broke ppoll */
#if !defined(__SNR_ppoll) && defined(__SNR_brk)
#ifdef __NR_ppoll
#define __SNR_ppoll __NR_ppoll
#else
#define __SNR_ppoll __PNR_ppoll
#endif
#endif
static const int syscall_whitelist[] = {
/* TODO ireg sem*() syscalls */
SCMP_SYS(brk),
SCMP_SYS(capget), /* For CAP_FSETID */
SCMP_SYS(capset),
SCMP_SYS(clock_gettime),
SCMP_SYS(clone),
#ifdef __NR_clone3
SCMP_SYS(clone3),
#endif
SCMP_SYS(close),
SCMP_SYS(copy_file_range),
SCMP_SYS(dup),
SCMP_SYS(eventfd2),
SCMP_SYS(exit),
SCMP_SYS(exit_group),
SCMP_SYS(fallocate),
SCMP_SYS(fchmodat),
SCMP_SYS(fchownat),
SCMP_SYS(fcntl),
SCMP_SYS(fdatasync),
SCMP_SYS(fgetxattr),
SCMP_SYS(flistxattr),
SCMP_SYS(flock),
SCMP_SYS(fremovexattr),
SCMP_SYS(fsetxattr),
SCMP_SYS(fstat),
SCMP_SYS(fstatfs),
SCMP_SYS(fsync),
SCMP_SYS(ftruncate),
SCMP_SYS(futex),
SCMP_SYS(getdents),
SCMP_SYS(getdents64),
SCMP_SYS(getegid),
SCMP_SYS(geteuid),
SCMP_SYS(getpid),
SCMP_SYS(gettid),
SCMP_SYS(gettimeofday),
SCMP_SYS(linkat),
SCMP_SYS(lseek),
SCMP_SYS(madvise),
SCMP_SYS(mkdirat),
SCMP_SYS(mknodat),
SCMP_SYS(mmap),
SCMP_SYS(mprotect),
SCMP_SYS(mremap),
SCMP_SYS(munmap),
SCMP_SYS(newfstatat),
SCMP_SYS(open),
SCMP_SYS(openat),
SCMP_SYS(ppoll),
SCMP_SYS(prctl), /* TODO restrict to just PR_SET_NAME? */
SCMP_SYS(preadv),
SCMP_SYS(pread64),
SCMP_SYS(pwritev),
SCMP_SYS(pwrite64),
SCMP_SYS(read),
SCMP_SYS(readlinkat),
SCMP_SYS(recvmsg),
SCMP_SYS(renameat),
SCMP_SYS(renameat2),
SCMP_SYS(rt_sigaction),
SCMP_SYS(rt_sigprocmask),
SCMP_SYS(rt_sigreturn),
SCMP_SYS(sendmsg),
SCMP_SYS(setresgid),
SCMP_SYS(setresuid),
#ifdef __NR_setresgid32
SCMP_SYS(setresgid32),
#endif
#ifdef __NR_setresuid32
SCMP_SYS(setresuid32),
#endif
SCMP_SYS(set_robust_list),
SCMP_SYS(symlinkat),
SCMP_SYS(time), /* Rarely needed, except on static builds */
SCMP_SYS(tgkill),
SCMP_SYS(unlinkat),
SCMP_SYS(utimensat),
SCMP_SYS(write),
SCMP_SYS(writev),
};
void setup_seccomp(void)
{
scmp_filter_ctx ctx;
size_t i;
#ifdef SCMP_ACT_KILL_PROCESS
ctx = seccomp_init(SCMP_ACT_KILL_PROCESS);
/* Handle a newer libseccomp but an older kernel */
if (!ctx && errno == EOPNOTSUPP) {
ctx = seccomp_init(SCMP_ACT_TRAP);
}
#else
ctx = seccomp_init(SCMP_ACT_TRAP);
#endif
if (!ctx) {
fuse_log(FUSE_LOG_ERR, "seccomp_init() failed\n");
exit(1);
}
for (i = 0; i < G_N_ELEMENTS(syscall_whitelist); i++) {
if (seccomp_rule_add(ctx, SCMP_ACT_ALLOW,
syscall_whitelist[i], 0) != 0) {
fuse_log(FUSE_LOG_ERR, "seccomp_rule_add syscall %d",
syscall_whitelist[i]);
exit(1);
}
}
/* libvhost-user calls this for post-copy migration, we don't need it */
if (seccomp_rule_add(ctx, SCMP_ACT_ERRNO(ENOSYS),
SCMP_SYS(userfaultfd), 0) != 0) {
fuse_log(FUSE_LOG_ERR, "seccomp_rule_add userfaultfd failed\n");
exit(1);
}
if (seccomp_load(ctx) < 0) {
fuse_log(FUSE_LOG_ERR, "seccomp_load() failed\n");
exit(1);
}
seccomp_release(ctx);
}

14
tools/virtiofsd/seccomp.h Normal file
View File

@ -0,0 +1,14 @@
/*
* Seccomp sandboxing for virtiofsd
*
* Copyright (C) 2019 Red Hat, Inc.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#ifndef VIRTIOFSD_SECCOMP_H
#define VIRTIOFSD_SECCOMP_H
void setup_seccomp(void);
#endif /* VIRTIOFSD_SECCOMP_H */