From: Stefan Hajnoczi <stefanha@redhat.com>

Date: Mon, 27 Jan 2020 19:01:30 +0000

Subject: [PATCH] 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>

(cherry picked from commit 4f8bde99c175ffd86b5125098a4707d43f5e80c6)

---

 Makefile                         |   5 +-

 tools/virtiofsd/Makefile.objs    |   5 +-

 tools/virtiofsd/passthrough_ll.c |   2 +

 tools/virtiofsd/seccomp.c        | 151 +++++++++++++++++++++++++++++++

 tools/virtiofsd/seccomp.h        |  14 +++

 5 files changed, 174 insertions(+), 3 deletions(-)

 create mode 100644 tools/virtiofsd/seccomp.c

 create mode 100644 tools/virtiofsd/seccomp.h

diff --git a/Makefile b/Makefile

index aebb57aed8..9a17e34603 100644

--- a/Makefile

+++ b/Makefile

@@ -330,7 +330,7 @@ endif

 endif

 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

@@ -680,7 +680,8 @@ 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

diff --git a/tools/virtiofsd/Makefile.objs b/tools/virtiofsd/Makefile.objs

index 45a807500d..076f667e46 100644

--- a/tools/virtiofsd/Makefile.objs

+++ b/tools/virtiofsd/Makefile.objs

@@ -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)

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c

index 0947d14e5b..bd8925bd83 100644

--- a/tools/virtiofsd/passthrough_ll.c

+++ b/tools/virtiofsd/passthrough_ll.c

@@ -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[])

diff --git a/tools/virtiofsd/seccomp.c b/tools/virtiofsd/seccomp.c

new file mode 100644

index 0000000000..691fb63dea

--- /dev/null

+++ b/tools/virtiofsd/seccomp.c

@@ -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);

+}

diff --git a/tools/virtiofsd/seccomp.h b/tools/virtiofsd/seccomp.h

new file mode 100644

index 0000000000..86bce72652

--- /dev/null

+++ b/tools/virtiofsd/seccomp.h

@@ -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 */