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Re: [libvirt] [PATCH] qemu: pass the information when disks are read-only



On Thu, Mar 11, 2010 at 06:14:01PM +0100, Daniel Veillard wrote:
> The problem is that even when the user indicates that a drive has to be
> opened as read-only (for example a cd-rom) qemu didn't get the
> information and tried to open read-write. This could get really nasty
> in case SELinux is monitoring that no read-write access is attempted:
> 
>   https://bugzilla.redhat.com/show_bug.cgi?id=536760
> 
> Patch is relatively simple and based on teh assumption that if the
> -device qemu options are allowed then qemu also knows about the
> readonly option (this was added to the help string quite later so
> we should not rely on that in this case).
> 
> * src/qemu/qemu_conf.c: add the ",readonly=on" for read-only disks
>   and also parse it back in qemuParseCommandLineDisk()
> * tests/qemuxml2argvtest.c
>   tests/qemuxml2argvdata/qemuxml2argv-disk-drive-readonly-disk.args
>   tests/qemuxml2argvdata/qemuxml2argv-disk-drive-readonly-disk.xml:
>   add a specific regression test
> 
> diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
> index 40ca221..fb23c52 100644
> --- a/src/qemu/qemu_conf.c
> +++ b/src/qemu/qemu_conf.c
> @@ -2398,6 +2398,9 @@ qemuBuildDriveStr(virDomainDiskDefPtr disk,
>      if (bootable &&
>          disk->device == VIR_DOMAIN_DISK_DEVICE_DISK)
>          virBufferAddLit(&opt, ",boot=on");
> +    if (disk->readonly &&
> +        qemuCmdFlags & QEMUD_CMD_FLAG_DEVICE)
> +        virBufferAddLit(&opt, ",readonly=on");
>      if (disk->driverType &&
>          disk->type != VIR_DOMAIN_DISK_TYPE_DIR &&
>          qemuCmdFlags & QEMUD_CMD_FLAG_DRIVE_FORMAT)
> @@ -4694,6 +4697,9 @@ qemuParseCommandLineDisk(const char *val,
>                                  _("cannot parse drive unit '%s'"), val);
>                  goto cleanup;
>              }
> +        } else if (STREQ(keywords[i], "readonly")) {
> +            if ((values[i] == NULL) || STREQ(values[i], "on"))
> +                def->readonly = 1;
>          }
>      }
>  
> diff --git a/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-readonly-disk.args b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-readonly-disk.args
> new file mode 100644
> index 0000000..fbc3226
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-readonly-disk.args
> @@ -0,0 +1 @@
> +LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/bin/qemu -S -M pc -m 214 -smp 1 -nographic -nodefaults -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c -drive file=/dev/HostVG/QEMUGuest1,if=none,id=drive-ide0-0-0 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -drive file=/dev/sr0,if=none,media=cdrom,id=drive-ide0-1-0,readonly=on -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -usb -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
> diff --git a/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-readonly-disk.xml b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-readonly-disk.xml
> new file mode 100644
> index 0000000..39c3a1c
> --- /dev/null
> +++ b/tests/qemuxml2argvdata/qemuxml2argv-disk-drive-readonly-disk.xml
> @@ -0,0 +1,30 @@
> +<domain type='qemu'>
> +  <name>QEMUGuest1</name>
> +  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
> +  <memory>219200</memory>
> +  <currentMemory>219200</currentMemory>
> +  <vcpu>1</vcpu>
> +  <os>
> +    <type arch='i686' machine='pc'>hvm</type>
> +    <boot dev='hd'/>
> +  </os>
> +  <clock offset='utc'/>
> +  <on_poweroff>destroy</on_poweroff>
> +  <on_reboot>restart</on_reboot>
> +  <on_crash>destroy</on_crash>
> +  <devices>
> +    <emulator>/usr/bin/qemu</emulator>
> +    <disk type='block' device='disk'>
> +      <source dev='/dev/HostVG/QEMUGuest1'/>
> +      <target dev='hda' bus='ide'/>
> +      <address type='drive' controller='0' bus='0' unit='0'/>
> +    </disk>
> +    <disk type='block' device='cdrom'>
> +       <source dev='/dev/sr0'/>
> +       <target dev='hdc' bus='ide'/>
> +       <readonly/>
> +       <address type='drive' controller='0' bus='1' unit='0'/>
> +    </disk>
> +    <controller type='ide' index='0'/>
> +  </devices>
> +</domain>
> diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
> index 4ca946a..e3762c9 100644
> --- a/tests/qemuxml2argvtest.c
> +++ b/tests/qemuxml2argvtest.c
> @@ -249,6 +249,8 @@ mymain(int argc, char **argv)
>              QEMUD_CMD_FLAG_DRIVE_BOOT | QEMUD_CMD_FLAG_DRIVE_FORMAT);
>      DO_TEST("disk-drive-fat", QEMUD_CMD_FLAG_DRIVE |
>              QEMUD_CMD_FLAG_DRIVE_BOOT | QEMUD_CMD_FLAG_DRIVE_FORMAT);
> +    DO_TEST("disk-drive-readonly-disk", QEMUD_CMD_FLAG_DRIVE |
> +            QEMUD_CMD_FLAG_DEVICE);
>      DO_TEST("disk-drive-fmt-qcow", QEMUD_CMD_FLAG_DRIVE |
>              QEMUD_CMD_FLAG_DRIVE_BOOT | QEMUD_CMD_FLAG_DRIVE_FORMAT);
>      DO_TEST("disk-drive-shared", QEMUD_CMD_FLAG_DRIVE |
> 

ACK, good to finally have this done

Daniel
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