Implement chroot server side interfaces like sending the file
descriptor to qemu process, reading the object request from socket etc.
Also add chroot main function and other helper routines.
Signed-off-by: M. Mohan Kumar <mo...@in.ibm.com>
---
Makefile.objs | 1 +
hw/9pfs/virtio-9p-chroot-sv.c | 169 +++++++++++++++++++++++++++++++++++++++++
hw/9pfs/virtio-9p-chroot.h | 57 ++++++++++++++
hw/9pfs/virtio-9p.c | 32 ++++++++
hw/file-op-9p.h | 4 +
5 files changed, 263 insertions(+), 0 deletions(-)
create mode 100644 hw/9pfs/virtio-9p-chroot-sv.c
create mode 100644 hw/9pfs/virtio-9p-chroot.h
diff --git a/Makefile.objs b/Makefile.objs
index f930cdd..bf8ebd9 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -282,6 +282,7 @@ hw-obj-$(CONFIG_SOUND) += $(sound-obj-y)
9pfs-nested-$(CONFIG_VIRTFS) = virtio-9p-debug.o
9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-local.o virtio-9p-xattr.o
9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-xattr-user.o virtio-9p-posix-acl.o
+9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-chroot-sv.o
hw-obj-$(CONFIG_REALLY_VIRTFS) += $(addprefix 9pfs/, $(9pfs-nested-y))
$(addprefix 9pfs/, $(9pfs-nested-y)): CFLAGS += -I$(SRC_PATH)/hw/
diff --git a/hw/9pfs/virtio-9p-chroot-sv.c b/hw/9pfs/virtio-9p-chroot-sv.c
new file mode 100644
index 0000000..86d10cd
--- /dev/null
+++ b/hw/9pfs/virtio-9p-chroot-sv.c
@@ -0,0 +1,169 @@
+/*
+ * Virtio 9p chroot environment for contained access to exported path
+ * Server side
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ * M. Mohan Kumar <mo...@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the copying file in the top-level directory
+ *
+ */
+
+#include <sys/fsuid.h>
+#include <sys/resource.h>
+#include <signal.h>
+#include "virtio.h"
+#include "qemu_socket.h"
+#include "qemu-thread.h"
+#include "qerror.h"
+#include "virtio-9p.h"
+#include "virtio-9p-chroot.h"
+
+/* Send file descriptor and error status to qemu process */
+static void chroot_sendfd(int sockfd, const FdInfo *fd_info)
+{
+ struct msghdr msg = { };
+ struct iovec iov;
+ struct cmsghdr *cmsg;
+ int retval;
+ union MsgControl msg_control;
+
+ iov.iov_base = (void *)fd_info;
+ iov.iov_len = sizeof(*fd_info);
+
+ memset(&msg, 0, sizeof(msg));
+ msg.msg_iov = &iov;
+ msg.msg_iovlen = 1;
+ /* No ancillary data on error/fd invalid flag */
+ if (fd_info->fi_flags & FI_FDVALID) {
+ msg.msg_control = &msg_control;
+ msg.msg_controllen = sizeof(msg_control);
+
+ cmsg = &msg_control.cmsg;
+ cmsg->cmsg_len = CMSG_LEN(sizeof(fd_info->fi_fd));
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ memcpy(CMSG_DATA(cmsg), &fd_info->fi_fd, sizeof(fd_info->fi_fd));
+ }
+ retval = sendmsg(sockfd, &msg, 0);
+ if (retval == EPIPE || retval == EBADF) {
+ _exit(1);
+ }
+ if (fd_info->fi_flags & FI_FDVALID) {
+ close(fd_info->fi_fd);
+ }
+}
+
+/* Read V9fsFileObjectRequest written by QEMU process */
+static int chroot_read_request(int sockfd, V9fsFileObjectRequest *request)
+{
+ int retval;
+ retval = qemu_read_full(sockfd, request, sizeof(*request));
+ if (retval != sizeof(*request)) {
+ if (errno == EBADF) {
+ _exit(1);
+ }
+ return EIO;
+ }
+ return 0;
+}
+
+static int chroot_daemonize(int chroot_sock)
+{
+ sigset_t sigset;
+ struct rlimit nr_fd;
+ int fd;
+
+ /* Block all signals for this process */
+ sigprocmask(SIG_SETMASK, &sigset, NULL);
+
+ /* Daemonize */
+ if (setsid() < 0) {
+ return errno;
+ }
+
+ /* Close other file descriptors */
+ getrlimit(RLIMIT_NOFILE, &nr_fd);
+ for (fd = 0; fd < nr_fd.rlim_cur; fd++) {
+ if (fd != chroot_sock) {
+ close(fd);
+ }
+ }
+ chdir("/");
+
+ /* Create files with mode as requested by client */
+ umask(0);
+ return 0;
+}
+
+/*
+ * Fork a process and chroot into the share path. Communication
+ * between qemu process and chroot process happens via socket.
+ * All file descriptors (including stdout and stderr) are closed
+ * except one socket descriptor (which is used for communicating
+ * between qemu process and chroot process).
+ * Note: To avoid errors in forked process in multi threaded environment
+ * use only async-signal safe functions only. For more information see
+ * man fork(3p), signal(7)
+ */
+int v9fs_chroot(FsContext *fs_ctx)
+{
+ int fd_pair[2], chroot_sock, error;
+ V9fsFileObjectRequest request;
+ pid_t pid;
+ uint64_t code;
+ FdInfo fd_info;
+
+ if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd_pair) < 0) {
+ error_report("socketpair %s", strerror(errno));
+ return -1;
+ }
+
+ pid = fork();
+ if (pid < 0) {
+ error_report("fork %s", strerror(errno));
+ return -1;
+ }
+ if (pid != 0) {
+ fs_ctx->chroot_socket = fd_pair[0];
+ close(fd_pair[1]);
+ return 0;
+ }
+
+ close(fd_pair[0]);
+ chroot_sock = fd_pair[1];
+ if (chroot(fs_ctx->fs_root) < 0) {
+ code = CHROOT_ERROR << 32 | errno;
+ error = qemu_write_full(chroot_sock, &code, sizeof(code));
+ _exit(1);
+ }
+
+ error = chroot_daemonize(chroot_sock);
+ if (error) {
+ code = SETSID_ERROR << 32 | error;
+ error = qemu_write_full(chroot_sock, &code, sizeof(code));
+ _exit(1);
+ }
+
+ /*
+ * Write 0 to chroot socket to indicate chroot process creation is
+ * successful
+ */
+ code = 0;
+ if (qemu_write_full(chroot_sock, &code, sizeof(code))
+ != sizeof(code)) {
+ _exit(1);
+ }
+ /* get the request from the socket */
+ while (1) {
+ memset(&fd_info, 0, sizeof(fd_info));
+ if (chroot_read_request(chroot_sock, &request) == EIO) {
+ fd_info.fi_fd = 0;
+ fd_info.fi_error = EIO;
+ fd_info.fi_flags = FI_SOCKERR;
+ chroot_sendfd(chroot_sock, &fd_info);
+ }
+ }
+}
diff --git a/hw/9pfs/virtio-9p-chroot.h b/hw/9pfs/virtio-9p-chroot.h
new file mode 100644
index 0000000..73cf144
--- /dev/null
+++ b/hw/9pfs/virtio-9p-chroot.h
@@ -0,0 +1,57 @@
+#ifndef _QEMU_VIRTIO_9P_CHROOT_H
+#define _QEMU_VIRTIO_9P_CHROOT_H
+
+/* types for V9fsFileObjectRequest */
+#define T_OPEN 1
+#define T_CREATE 2
+#define T_MKDIR 3
+#define T_MKNOD 4
+#define T_SYMLINK 5
+#define T_LINK 6
+#define CHROOT_ERROR 1ULL
+#define SETSID_ERROR 2ULL
+
+/*
+ * Structure used by chroot functions to transmit file descriptor and
+ * error info
+ */
+typedef struct {
+ int fi_fd;
+#define FI_FDVALID 1
+#define FI_SOCKERR 2
+ int fi_flags;
+ int fi_error;
+} FdInfo;
+
+union MsgControl {
+ struct cmsghdr cmsg;
+ char control[CMSG_SPACE(sizeof(int))];
+};
+
+struct V9fsFileObjectData
+{
+ int flags;
+ int mode;
+ uid_t uid;
+ gid_t gid;
+ dev_t dev;
+ int path_len;
+ int oldpath_len;
+ int type;
+};
+
+struct V9fsFileObjectPath
+{
+ char path[PATH_MAX];
+ char old_path[PATH_MAX];
+};
+
+typedef struct V9fsFileObjectRequest
+{
+ struct V9fsFileObjectData data;
+ struct V9fsFileObjectPath path;
+} V9fsFileObjectRequest;
+
+int v9fs_chroot(FsContext *fs_ctx);
+
+#endif /* _QEMU_VIRTIO_9P_CHROOT_H */
diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
index 27e7750..3aff70b 100644
--- a/hw/9pfs/virtio-9p.c
+++ b/hw/9pfs/virtio-9p.c
@@ -14,10 +14,12 @@
#include "virtio.h"
#include "pc.h"
#include "qemu_socket.h"
+#include "qerror.h"
#include "virtio-9p.h"
#include "fsdev/qemu-fsdev.h"
#include "virtio-9p-debug.h"
#include "virtio-9p-xattr.h"
+#include "virtio-9p-chroot.h"
int debug_9p_pdu;
@@ -3743,5 +3745,35 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf
*conf)
s->tag_len;
s->vdev.get_config = virtio_9p_get_config;
+ if (s->ctx.fs_sm == SM_PASSTHROUGH) {
+ uint64_t code;
+ qemu_mutex_init(&s->ctx.chroot_mutex);
+ s->ctx.chroot_ioerror = 0;
+ if (v9fs_chroot(&s->ctx) < 0) {
+ exit(1);
+ }
+
+ /*
+ * Chroot process sends 0 to indicate chroot process creation is
+ * successful
+ */
+ if (read(s->ctx.chroot_socket, &code, sizeof(code)) != sizeof(code)) {
+ error_report("chroot process creation failed");
+ exit(1);
+ }
+ if (code != 0) {
+ switch (code >> 32) {
+ case CHROOT_ERROR:
+ error_report("chroot system call failed: %s",
+ strerror(code & 0xFFFFFFFF));
+ break;
+ case SETSID_ERROR:
+ error_report("setsid failed: %s", strerror(code & 0xFFFFFFFF));
+ break;
+ }
+ exit(1);
+ }
+ }
+
return &s->vdev;
}
diff --git a/hw/file-op-9p.h b/hw/file-op-9p.h
index 126e60e..b52b432 100644
--- a/hw/file-op-9p.h
+++ b/hw/file-op-9p.h
@@ -19,6 +19,7 @@
#include <sys/stat.h>
#include <sys/uio.h>
#include <sys/vfs.h>
+#include "qemu-thread.h"
#define SM_LOCAL_MODE_BITS 0600
#define SM_LOCAL_DIR_MODE_BITS 0700
@@ -55,6 +56,9 @@ typedef struct FsContext
SecModel fs_sm;
uid_t uid;
struct xattr_operations **xops;
+ QemuMutex chroot_mutex;
+ int chroot_socket;
+ int chroot_ioerror;
} FsContext;
void cred_init(FsCred *);
--
1.7.3.4
