[Qemu-devel] [PATCH V5 14/14] hw/9pfs: Add support to use named socket for proxy FS

["M. Mohan Kumar" <mohan@in.ibm.com>]

From: "M. Mohan Kumar" <mohan@in.ibm.com>

Add option to use named socket for communicating between proxy helper
and qemu proxy FS. Access to socket can be given by using command line
options -u and -g. We can achive the same using a shell script over
qemu and virtfs-proxy-helper using exec fd<><socket-path>, and then
passing that fd as argument to qemu and virtfs-proxy-helper. Also having
a server like virtfs-proxy-helper listening on a pathname without any
authentication is little bit scary. So we have to decide whether this
patch is really needed.

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fsdev/file-op-9p.h             |    2 +
 fsdev/virtfs-proxy-helper.c    |   86 ++++++++++++++++++++++++++++++++++++++-
 fsdev/virtfs-proxy-helper.texi |    4 ++
 hw/9pfs/virtio-9p-proxy.c      |   52 +++++++++++++++++++++---
 qemu-config.c                  |    7 +++
 qemu-options.hx                |   15 +++++--
 vl.c                           |    6 ++-
 7 files changed, 157 insertions(+), 15 deletions(-)

diff --git a/fsdev/file-op-9p.h b/fsdev/file-op-9p.h
index 73de79f..4f76f9d 100644
--- a/fsdev/file-op-9p.h
+++ b/fsdev/file-op-9p.h
@@ -57,6 +57,8 @@ typedef struct extended_ops {
  */
 #define V9FS_SM_NONE                0x00000010
 #define V9FS_RDONLY                 0x00000020
+#define V9FS_PROXY_SOCK_FD          0x00000040
+#define V9FS_PROXY_SOCK_NAME        0x00000080
 
 #define V9FS_SEC_MASK               0x0000001C
 
diff --git a/fsdev/virtfs-proxy-helper.c b/fsdev/virtfs-proxy-helper.c
index 3beed25..baafee2 100644
--- a/fsdev/virtfs-proxy-helper.c
+++ b/fsdev/virtfs-proxy-helper.c
@@ -57,6 +57,9 @@ static struct option helper_opts[] = {
     {"fd", required_argument, NULL, 'f'},
     {"path", required_argument, NULL, 'p'},
     {"nodaemon", no_argument, NULL, 'n'},
+    {"socket", required_argument, NULL, 's'},
+    {"uid", required_argument, NULL, 'u'},
+    {"gid", required_argument, NULL, 'g'},
 };
 
 static bool is_daemon;
@@ -690,11 +693,61 @@ err_out:
     return ret;
 }
 
+/* create unix domain socket and return the descriptor */
+static int proxy_socket(const char *path, uid_t uid, gid_t gid)
+{
+    int sock, client;
+    struct sockaddr_un proxy, qemu;
+    socklen_t size;
+
+    /* requested socket already exists, refuse to start */
+    if (!access(path, F_OK)) {
+        do_log(LOG_CRIT, "socket already exists\n");
+        return -1;
+    }
+
+    sock = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (sock < 0) {
+        do_perror("socket");
+        return -1;
+    }
+
+    /* mask other part of mode bits */
+    umask(7);
+
+    proxy.sun_family = AF_UNIX;
+    strcpy(proxy.sun_path, path);
+    if (bind(sock, (struct sockaddr *)&proxy,
+            sizeof(struct sockaddr_un)) < 0) {
+        do_perror("bind");
+        return -1;
+    }
+    if (chown(proxy.sun_path, uid, gid) < 0) {
+        do_perror("chown");
+        return -1;
+    }
+    if (listen(sock, 1) < 0) {
+        do_perror("listen");
+        return -1;
+    }
+
+    client = accept(sock, (struct sockaddr *)&qemu, &size);
+    if (client < 0) {
+        do_perror("accept");
+        return -1;
+    }
+    return client;
+}
+
 static void usage(char *prog)
 {
     fprintf(stderr, "usage: %s\n"
             " -p|--path <path> 9p path to export\n"
             " {-f|--fd <socket-descriptor>} socket file descriptor to be used\n"
+            " {-s|--socket <socketname> socket file used for communication\n"
+            " \t-u|--uid <uid> -g|--gid <gid>} - uid:gid combination to give "
+            " access to this socket\n"
+            " \tNote: -s & -f can not be used together\n"
             " [-n|--nodaemon] Run as a normal program\n",
             basename(prog));
 }
@@ -935,16 +988,20 @@ int main(int argc, char **argv)
 {
     int sock;
     char *rpath = NULL;
+    char *sock_name = NULL;
     struct stat stbuf;
     int c, option_index;
     int retval;
     struct statfs st_fs;
+    uid_t own_u;
+    gid_t own_g;
 
     is_daemon = true;
     sock = -1;
+    own_u = own_g = -1;
     while (1) {
         option_index = 0;
-        c = getopt_long(argc, argv, "p:nh?f:", helper_opts,
+        c = getopt_long(argc, argv, "p:nh?f:s:u:g:", helper_opts,
                         &option_index);
         if (c == -1) {
             break;
@@ -959,6 +1016,15 @@ int main(int argc, char **argv)
         case 'f':
             sock = atoi(optarg);
             break;
+        case 's':
+            sock_name = strdup(optarg);
+            break;
+        case 'u':
+            own_u = atoi(optarg);
+            break;
+        case 'g':
+            own_g = atoi(optarg);
+            break;
         case '?':
         case 'h':
         default:
@@ -968,8 +1034,16 @@ int main(int argc, char **argv)
     }
 
     /* Parameter validation */
-    if (sock == -1 || rpath == NULL) {
-        fprintf(stderr, "socket descriptor or path not specified\n");
+    if ((sock_name == NULL && sock == -1) || rpath == NULL) {
+        fprintf(stderr, "socket, socket descriptor or path not specified\n");
+        usage(argv[0]);
+        return -1;
+    }
+
+    if (*sock_name && (own_u == -1 || own_g == -1)) {
+        fprintf(stderr, "owner uid:gid not specified, ");
+        fprintf(stderr,
+                "owner uid:gid specifies who can access the socket file\n");
         usage(argv[0]);
         exit(EXIT_FAILURE);
     }
@@ -994,6 +1068,12 @@ int main(int argc, char **argv)
     }
 
     do_log(LOG_INFO, "Started\n");
+    if (*sock_name) {
+        sock = proxy_socket(sock_name, own_u, own_g);
+        if (sock < 0) {
+            goto error;
+        }
+    }
 
     get_version = false;
 #ifdef FS_IOC_GETVERSION
diff --git a/fsdev/virtfs-proxy-helper.texi b/fsdev/virtfs-proxy-helper.texi
index 3816382..faa0434 100644
--- a/fsdev/virtfs-proxy-helper.texi
+++ b/fsdev/virtfs-proxy-helper.texi
@@ -46,6 +46,10 @@ Path to export for proxy filesystem driver
 Use given file descriptor as socket descriptor for communicating with
 qemu proxy fs drier. Usually a helper like libvirt will create
 socketpair and pass one of the fds as parameter to -f|--fd
+@item -s|--socket socket-file
+Creates named socket file for communicating with qemu proxy fs driver
+@item -u|--uid uid -g|--gid gid
+uid:gid combination to give access to named socket file
 @item -n|--nodaemon
 Run as a normal program. By default program will run in daemon mode
 @end table
diff --git a/hw/9pfs/virtio-9p-proxy.c b/hw/9pfs/virtio-9p-proxy.c
index e782c4f..d94db95 100644
--- a/hw/9pfs/virtio-9p-proxy.c
+++ b/hw/9pfs/virtio-9p-proxy.c
@@ -1095,15 +1095,49 @@ static int proxy_ioc_getversion(FsContext *fs_ctx, V9fsPath *path,
     return err;
 }
 
+static int connect_namedsocket(const char *path)
+{
+    int sockfd, size;
+    struct sockaddr_un helper;
+
+    sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (sockfd < 0) {
+        fprintf(stderr, "socket %s\n", strerror(errno));
+        return -1;
+    }
+    strcpy(helper.sun_path, path);
+    helper.sun_family = AF_UNIX;
+    size = strlen(helper.sun_path) + sizeof(helper.sun_family);
+    if (connect(sockfd, (struct sockaddr *)&helper, size) < 0) {
+        fprintf(stderr, "socket error\n");
+        return -1;
+    }
+
+    /* remove the socket for security reasons */
+    unlink(path);
+    return sockfd;
+}
+
 static int proxy_parse_opts(QemuOpts *opts, struct FsDriverEntry *fs)
 {
+    const char *socket = qemu_opt_get(opts, "socket");
     const char *sock_fd = qemu_opt_get(opts, "sock_fd");
 
-    if (sock_fd) {
-        fprintf(stderr, "sock_fd option not specified\n");
+    if (!socket && !sock_fd) {
+        fprintf(stderr, "socket and sock_fd none of the option specified\n");
+        return -1;
+    }
+    if (socket && sock_fd) {
+        fprintf(stderr, "Both socket and sock_fd options specified\n");
         return -1;
     }
-    fs->path = g_strdup(sock_fd);
+    if (socket) {
+        fs->path = g_strdup(socket);
+        fs->export_flags = V9FS_PROXY_SOCK_NAME;
+    } else {
+        fs->path = g_strdup(sock_fd);
+        fs->export_flags = V9FS_PROXY_SOCK_FD;
+    }
     return 0;
 }
 
@@ -1112,10 +1146,14 @@ static int proxy_init(FsContext *ctx)
     V9fsProxy *proxy = g_malloc(sizeof(V9fsProxy));
     int sock_id;
 
-    sock_id = atoi(ctx->fs_root);
-    if (sock_id < 0) {
-        fprintf(stderr, "socket descriptor not initialized\n");
-        return -1;
+    if (ctx->export_flags & V9FS_PROXY_SOCK_NAME) {
+        sock_id = connect_namedsocket(ctx->fs_root);
+    } else {
+        sock_id = atoi(ctx->fs_root);
+        if (sock_id < 0) {
+            fprintf(stderr, "socket descriptor not initialized\n");
+            return -1;
+        }
     }
     g_free(ctx->fs_root);
 
diff --git a/qemu-config.c b/qemu-config.c
index 1bdc01c..ecc88e8 100644
--- a/qemu-config.c
+++ b/qemu-config.c
@@ -211,6 +211,10 @@ QemuOptsList qemu_fsdev_opts = {
         }, {
             .name = "readonly",
             .type = QEMU_OPT_BOOL,
+
+        }, {
+            .name = "socket",
+            .type = QEMU_OPT_STRING,
         }, {
             .name = "sock_fd",
             .type = QEMU_OPT_NUMBER,
@@ -244,6 +248,9 @@ QemuOptsList qemu_virtfs_opts = {
             .name = "readonly",
             .type = QEMU_OPT_BOOL,
         }, {
+            .name = "socket",
+            .type = QEMU_OPT_STRING,
+        }, {
             .name = "sock_fd",
             .type = QEMU_OPT_NUMBER,
         },
diff --git a/qemu-options.hx b/qemu-options.hx
index cfc999f..85c2440 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -539,12 +539,12 @@ DEFHEADING(File system options:)
 
 DEF("fsdev", HAS_ARG, QEMU_OPTION_fsdev,
     "-fsdev fsdriver,id=id[,path=path,][security_model={mapped|passthrough|none}]\n"
-    " [,writeout=immediate][,readonly][,sock_fd=sock_fd]\n",
+    " [,writeout=immediate][,readonly][,socket=socket|sock_fd=sock_fd]\n",
     QEMU_ARCH_ALL)
 
 STEXI
 
-@item -fsdev @var{fsdriver},id=@var{id},path=@var{path},[security_model=@var{security_model}][,writeout=@var{writeout}][,readonly][,sock_fd=@var{sock_fd}]
+@item -fsdev @var{fsdriver},id=@var{id},path=@var{path},[security_model=@var{security_model}][,writeout=@var{writeout}][,readonly][,socket=@var{socket}|sock_fd=@var{sock_fd}]
 @findex -fsdev
 Define a new file system device. Valid options are:
 @table @option
@@ -577,6 +577,9 @@ reported as written by the storage subsystem.
 @item readonly
 Enables exporting 9p share as a readonly mount for guests. By default
 read-write access is given.
+@item socket=@var{socket}
+Enables proxy filesystem driver to use passed socket file for communicating
+with virtfs-proxy-helper
 @item sock_fd=@var{sock_fd}
 Enables proxy filesystem driver to use passed socket descriptor for
 communicating with virtfs-proxy-helper. Usually a helper like libvirt
@@ -601,12 +604,12 @@ DEFHEADING(Virtual File system pass-through options:)
 
 DEF("virtfs", HAS_ARG, QEMU_OPTION_virtfs,
     "-virtfs local,path=path,mount_tag=tag,security_model=[mapped|passthrough|none]\n"
-    "        [,writeout=immediate][,readonly][,sock_fd=sock_fd]\n",
+    "        [,writeout=immediate][,readonly][,socket=socket|sock_fd=sock_fd]\n",
     QEMU_ARCH_ALL)
 
 STEXI
 
-@item -virtfs @var{fsdriver}[,path=@var{path}],mount_tag=@var{mount_tag}[,security_model=@var{security_model}][,writeout=@var{writeout}][,readonly][,sock_fd=@var{sock_fd}]
+@item -virtfs @var{fsdriver}[,path=@var{path}],mount_tag=@var{mount_tag}[,security_model=@var{security_model}][,writeout=@var{writeout}][,readonly][,socket=@var{socket}|sock_fd=@var{sock_fd}]
 @findex -virtfs
 
 The general form of a Virtual File system pass-through options are:
@@ -640,6 +643,10 @@ reported as written by the storage subsystem.
 @item readonly
 Enables exporting 9p share as a readonly mount for guests. By default
 read-write access is given.
+@item socket=@var{socket}
+Enables proxy filesystem driver to use passed socket file for
+communicating with virtfs-proxy-helper. Usually a helper like libvirt
+will create socketpair and pass one of the fds as sock_fd
 @item sock_fd
 Enables proxy filesystem driver to use passed 'sock_fd' as the socket
 descriptor for interfacing with virtfs-proxy-helper
diff --git a/vl.c b/vl.c
index 6323361..e553c2c 100644
--- a/vl.c
+++ b/vl.c
@@ -2669,7 +2669,7 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_virtfs: {
                 QemuOpts *fsdev;
                 QemuOpts *device;
-                const char *writeout, *sock_fd;
+                const char *writeout, *sock_fd, *socket;
 
                 olist = qemu_find_opts("virtfs");
                 if (!olist) {
@@ -2709,6 +2709,10 @@ int main(int argc, char **argv, char **envp)
                 qemu_opt_set(fsdev, "path", qemu_opt_get(opts, "path"));
                 qemu_opt_set(fsdev, "security_model",
                              qemu_opt_get(opts, "security_model"));
+                socket = qemu_opt_get(opts, "socket");
+                if (socket) {
+                    qemu_opt_set(fsdev, "socket", socket);
+                }
                 sock_fd = qemu_opt_get(opts, "sock_fd");
                 if (sock_fd) {
                     qemu_opt_set(fsdev, "sock_fd", sock_fd);
-- 
1.7.6