To use virtio-serial device, unix socket created for chardev with default umask(022) has insufficient permissions. e.g. start kvm guest with: -device virtio-serial \ -chardev socket,path=/tmp/foo,server,nowait,id=foo \ -device virtserialport,chardev=foo,name=org.fedoraproject.port.0 Check permissions for the socket file that has been created in the host to enable communication through virtual serial ports in the guest: #ls -l /tmp/somefile.sock srwxr-xr-x 1 qemu qemu 0 21. Jul 14:19 /tmp/somefile.sock Other users in the qemu group (like real user, test engines, etc) cannot write to this socket. Problem reported here: https://sourceware.org/bugzilla/show_bug.cgi?id=13078#c11 https://bugzilla.novell.com/show_bug.cgi?id=888166 This patch tries to add a 'umask' option to 'chardev', so that user can have chance to indicate a umask overwritting the default one (default is 022), then create unix sockets with expected permissions. Signed-off-by: Chunyan Liu <cyliu(a)suse.com&gt; --- This is patch for qemu. qemu-char.c | 3 +++ qemu-options.hx | 9 +++++++-- util/qemu-sockets.c | 12 +++++++++++- 3 files changed, 21 insertions(+), 3 deletions(-) diff --git a/qemu-char.c b/qemu-char.c index d4f327a..a39a5e4 100644 --- a/qemu-char.c +++ b/qemu-char.c @@ -3856,6 +3856,9 @@ QemuOptsList qemu_chardev_opts = { },{ .name = "chardev", .type = QEMU_OPT_STRING, + },{ + .name = "umask", + .type = QEMU_OPT_NUMBER, }, { /* end of list */ } }, diff --git a/qemu-options.hx b/qemu-options.hx index ecd0e34..078e9db 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -1929,7 +1929,7 @@ DEF("chardev", HAS_ARG, QEMU_OPTION_chardev, "-chardev null,id=id[,mux=on|off]\n" "-chardev socket,id=id[,host=host],port=port[,to=to][,ipv4][,ipv6][,nodelay]\n" " [,server][,nowait][,telnet][,mux=on|off] (tcp)\n" - "-chardev socket,id=id,path=path[,server][,nowait][,telnet],[mux=on|off] (unix)\n" + "-chardev socket,id=id,path=path[,umask][,server][,nowait][,telnet],[mux=on|off] (unix)\n" "-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr]\n" " [,localport=localport][,ipv4][,ipv6][,mux=on|off]\n" "-chardev msmouse,id=id[,mux=on|off]\n" @@ -2001,12 +2001,17 @@ Options to each backend are described below. A void device. This device will not emit any data, and will drop any data it receives. The null backend does not take any options. -@item -chardev socket ,id=@var{id} [@var{TCP options} or @var{unix options}] [,server] [,nowait] [,telnet] +@item -chardev socket ,id=@var{id} [@var{TCP options} or @var{unix options}] [,umask][,server] [,nowait] [,telnet] Create a two-way stream socket, which can be either a TCP or a unix socket. A unix socket will be created if @option{path} is specified. Behaviour is undefined if TCP options are specified for a unix socket. +@option{umask} specifies the umask used for creating a unix socket. Without +this option, default umask(022) will be used, permission is not sufficient +for virtio-serial device. One can indicate umask=0x002 for virtio-serial +device for correct usage. + @option{server} specifies that the socket shall be a listening socket. @option{nowait} specifies that QEMU should not block waiting for a client to diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index 5d38395..facf2c6 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -680,7 +680,8 @@ int unix_listen_opts(QemuOpts *opts, Error **errp) { struct sockaddr_un un; const char *path = qemu_opt_get(opts, "path"); - int sock, fd; + int newmask = qemu_opt_get_number(opts, "umask", 0); + int sock, fd, oldmask; sock = qemu_socket(PF_UNIX, SOCK_STREAM, 0); if (sock < 0) { @@ -708,10 +709,19 @@ int unix_listen_opts(QemuOpts *opts, Error **errp) } unlink(un.sun_path); + if (newmask) { + oldmask = umask(newmask); + } if (bind(sock, (struct sockaddr*) &un, sizeof(un)) < 0) { + if (newmask) { + umask(oldmask); + } error_set_errno(errp, errno, QERR_SOCKET_BIND_FAILED); goto err; } + if (newmask) { + umask(oldmask); + } if (listen(sock, 1) < 0) { error_set_errno(errp, errno, QERR_SOCKET_LISTEN_FAILED); goto err; -- 1.8.5.2

"Daniel P. Berrange" <berrange(a)redhat.com&gt; wrote: I think that's OK. Only one thing: I'm not sure if permissions of any other file created in qemu will be changed due to this change, and if that is unexpected or not.

"Daniel P. Berrange" <berrange(a)redhat.com&gt; wrote: I agree. Now suppose when it explicitly sets the mode S_IWGRP while creating new file, group user writing permission is really expected, I think setting umask to 002 to the whole qemu process should be OK.

To use virtio-serial device, unix socket created for communication with default umask(022) has insufficient permissions. e.g. 1. Setup a virtual machine with a virtio-serial device: # virsh edit myvm (...) <channel type='unix'> <source mode='bind' path='/tmp/somefile.sock'/> <target type='virtio' name='com.suse.sometest'/> <address type='virtio-serial' controller='0' bus='0' port='1'/> </channel> (...) <controller type='virtio-serial' index='0'> <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/> </controller> 2. Start this virtual machine: # virsh start myvm 3. Check permissions for the socket file that has been created in the host to enable communication through virtual serial ports in the guest: # ls -l /tmp/somefile.sock srwxr-xr-x 1 qemu qemu 0 21. Jul 14:19 /tmp/somefile.sock Other users in the qemu group (like real user, test engines, etc) cannot write to this socket. Problem reported here: https://sourceware.org/bugzilla/show_bug.cgi?id=13078#c11 https://bugzilla.novell.com/show_bug.cgi?id=888166 This patch tries to pass a 'umask' option to '-chardev' when building qemu command line in above configuration case. In qemu side, there is another patch to handle the 'umask' option to overwrite default umask(022). With these changes, unix socket created for virtio-serial device can have expected permissions. Signed-off-by: Chunyan Liu <cyliu(a)suse.com&gt; --- This is patch for libvirt. src/qemu/qemu_command.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index beb8ca8..11eee44 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -8509,6 +8509,18 @@ qemuBuildCommandLine(virConnectPtr conn, channel->info.alias, qemuCaps))) goto error; + /* use umask(002) instead of default umask(022) to create + * a unix socket, so that virtio-serial device has sufficient + * permissions for correct usage. + */ + if (channel->source.type == VIR_DOMAIN_CHR_TYPE_UNIX) { + char *tmpstr = NULL; + if (virAsprintf(&tmpstr, "%s,umask=0x002", devstr) < 0) + goto error; + VIR_FREE(devstr); + devstr = tmpstr; + } + virCommandAddArg(cmd, devstr); VIR_FREE(devstr); } -- 1.8.4.5