qemu-kvm/kvm-virtiofsd-add-seccomp-whitelist.patch

From 58c4e9473b364fb62aac797b0d69fd8ddb02c8c7 Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Mon, 27 Jan 2020 19:01:30 +0100
Subject: [PATCH 059/116] virtiofsd: add seccomp whitelist
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RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: <20200127190227.40942-56-dgilbert@redhat.com>
Patchwork-id: 93511
O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 055/112] virtiofsd: add seccomp whitelist
Bugzilla: 1694164
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Sergio Lopez Pascual <slp@redhat.com>

From: Stefan Hajnoczi <stefanha@redhat.com>

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)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 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 0e9755d..6879a06 100644
--- a/Makefile
+++ b/Makefile
@@ -330,7 +330,7 @@ endif
 endif
 endif
 
-ifdef CONFIG_LINUX
+ifeq ($(CONFIG_LINUX)$(CONFIG_SECCOMP),yy)
 HELPERS-y += virtiofsd$(EXESUF)
 vhost-user-json-y += tools/virtiofsd/50-qemu-virtiofsd.json
 endif
@@ -681,7 +681,8 @@ rdmacm-mux$(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 45a8075..076f667 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 0947d14..bd8925b 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 0000000..691fb63
--- /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 0000000..86bce72
--- /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 */
-- 
1.8.3.1