| Message ID | 1409643643-31589-2-git-send-email-cyliu@suse.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Sep 02, 2014 at 03:40:42PM +0800, Chunyan Liu wrote: > 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@suse.com> > --- > 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/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); > + } Setting umask() is not thread-safe as it affects the entire process. While this is OK for chardevs which are cold-plugged at startup, once QEMU is running it is not OK to alter umask during hotplug of devices. Wouldn't it be simpler for libvirt to simply set the umask to 002 when it first launches QEMU, avoiding the need for trying todo this per device. Regards, Daniel
>>> On 9/2/2014 at 04:54 PM, in message <20140902085434.GA21282@redhat.com>, "Daniel P. Berrange" <berrange@redhat.com> wrote: > On Tue, Sep 02, 2014 at 03:40:42PM +0800, Chunyan Liu wrote: > > 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@suse.com> > > --- > > 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/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); > > + } > > Setting umask() is not thread-safe as it affects the entire process. While > this is OK for chardevs which are cold-plugged at startup, once QEMU is > running it is not OK to alter umask during hotplug of devices. > > Wouldn't it be simpler for libvirt to simply set the umask to 002 when it > first launches QEMU, avoiding the need for trying todo this per device. 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. > > Regards, > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ > :| > |: http://libvirt.org -o- http://virt-manager.org > :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ > :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc > :| > > >
On Tue, Sep 02, 2014 at 03:08:51AM -0600, Chun Yan Liu wrote: > > > >>> On 9/2/2014 at 04:54 PM, in message <20140902085434.GA21282@redhat.com>, > "Daniel P. Berrange" <berrange@redhat.com> wrote: > > On Tue, Sep 02, 2014 at 03:40:42PM +0800, Chunyan Liu wrote: > > > 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@suse.com> > > > --- > > > 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/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); > > > + } > > > > Setting umask() is not thread-safe as it affects the entire process. While > > this is OK for chardevs which are cold-plugged at startup, once QEMU is > > running it is not OK to alter umask during hotplug of devices. > > > > Wouldn't it be simpler for libvirt to simply set the umask to 002 when it > > first launches QEMU, avoiding the need for trying todo this per device. > > 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. Whether or not it causes problems today is only half the story. I'm more concerned about the long term problems. The use of threads is increasing in QEMU over time, so manipulating umask() is a time-bomb waiting to strike at some point in the future when people have forgotten that this proposed feature exists. IMHO umask() should simply never be used when multiple threads are running, to avoid this long term risk entirely. Regards, Daniel
>>> On 9/2/2014 at 05:16 PM, in message <20140902091655.GB21282@redhat.com>, "Daniel P. Berrange" <berrange@redhat.com> wrote: > On Tue, Sep 02, 2014 at 03:08:51AM -0600, Chun Yan Liu wrote: > > > > > > >>> On 9/2/2014 at 04:54 PM, in message <20140902085434.GA21282@redhat.com>, > > "Daniel P. Berrange" <berrange@redhat.com> wrote: > > > On Tue, Sep 02, 2014 at 03:40:42PM +0800, Chunyan Liu wrote: > > > > 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@suse.com> > > > > --- > > > > 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/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); > > > > + } > > > > > > Setting umask() is not thread-safe as it affects the entire process. > While > > > this is OK for chardevs which are cold-plugged at startup, once QEMU is > > > running it is not OK to alter umask during hotplug of devices. > > > > > > Wouldn't it be simpler for libvirt to simply set the umask to 002 when it > > > first launches QEMU, avoiding the need for trying todo this per device. > > > > 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. > > Whether or not it causes problems today is only half the story. I'm more > concerned about the long term problems. The use of threads is increasing > in QEMU over time, so manipulating umask() is a time-bomb waiting to strike > at some point in the future when people have forgotten that this proposed > feature exists. IMHO umask() should simply never be used when multiple > threads are running, to avoid this long term risk entirely. 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. > > Regards, > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ > :| > |: http://libvirt.org -o- http://virt-manager.org > :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ > :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc > :| > > >
"Daniel P. Berrange" <berrange@redhat.com> writes: > On Tue, Sep 02, 2014 at 03:40:42PM +0800, Chunyan Liu wrote: >> 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@suse.com> >> --- >> 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/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); >> + } > > Setting umask() is not thread-safe as it affects the entire process. While > this is OK for chardevs which are cold-plugged at startup, once QEMU is > running it is not OK to alter umask during hotplug of devices. Indeed. No telling what else could be affected while the temporary umask is in effect. > Wouldn't it be simpler for libvirt to simply set the umask to 002 when it > first launches QEMU, avoiding the need for trying todo this per device. I guess that's okay as long as you also make sure QEMU's effective group is sane. If you must have laxer permissions just for a specific character device, you can perhaps chmod() after creating it. No good for tightening permissions, of course.
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;
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@suse.com> --- 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(-)