[PATCH] parport: buffer overflow fix
Fix potential buffer overflow in case the device ID did not end in semicolon. Also might fail to negotiate back to IEEE1284_MODE_COMPAT in case of failure. parport_device_id did not return what Documentation/parport-lowlevel.txt said, so I changed it to match it. Determining device ID length is overly complicated, but Tim Waugh recalled on linux-parport seeing some buggy device that might need it. Signed-off-by: Marko Kohtala <marko.kohtala@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Marko Kohtala
Linus Torvalds
parent
39ee059aff
commit
c660629059
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@ -128,8 +128,131 @@ static void parse_data(struct parport *port, int device, char *str)
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kfree(txt);
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}
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/* Read up to count-1 bytes of device id. Terminate buffer with
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* '\0'. Buffer begins with two Device ID length bytes as given by
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* device. */
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static ssize_t parport_read_device_id (struct parport *port, char *buffer,
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size_t count)
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{
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unsigned char length[2];
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unsigned lelen, belen;
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size_t idlens[4];
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unsigned numidlens;
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unsigned current_idlen;
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ssize_t retval;
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size_t len;
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/* First two bytes are MSB,LSB of inclusive length. */
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retval = parport_read (port, length, 2);
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if (retval < 0)
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return retval;
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if (retval != 2)
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return -EIO;
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if (count < 2)
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return 0;
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memcpy(buffer, length, 2);
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len = 2;
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/* Some devices wrongly send LE length, and some send it two
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* bytes short. Construct a sorted array of lengths to try. */
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belen = (length[0] << 8) + length[1];
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lelen = (length[1] << 8) + length[0];
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idlens[0] = min(belen, lelen);
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idlens[1] = idlens[0]+2;
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if (belen != lelen) {
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int off = 2;
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/* Don't try lenghts of 0x100 and 0x200 as 1 and 2 */
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if (idlens[0] <= 2)
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off = 0;
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idlens[off] = max(belen, lelen);
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idlens[off+1] = idlens[off]+2;
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numidlens = off+2;
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}
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else {
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/* Some devices don't truly implement Device ID, but
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* just return constant nibble forever. This catches
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* also those cases. */
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if (idlens[0] == 0 || idlens[0] > 0xFFF) {
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printk (KERN_DEBUG "%s: reported broken Device ID"
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" length of %#zX bytes\n",
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port->name, idlens[0]);
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return -EIO;
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}
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numidlens = 2;
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}
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/* Try to respect the given ID length despite all the bugs in
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* the ID length. Read according to shortest possible ID
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* first. */
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for (current_idlen = 0; current_idlen < numidlens; ++current_idlen) {
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size_t idlen = idlens[current_idlen];
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if (idlen+1 >= count)
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break;
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retval = parport_read (port, buffer+len, idlen-len);
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if (retval < 0)
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return retval;
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len += retval;
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if (port->physport->ieee1284.phase != IEEE1284_PH_HBUSY_DAVAIL) {
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if (belen != len) {
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printk (KERN_DEBUG "%s: Device ID was %d bytes"
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" while device told it would be %d"
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" bytes\n",
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port->name, len, belen);
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}
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goto done;
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}
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/* This might end reading the Device ID too
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* soon. Hopefully the needed fields were already in
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* the first 256 bytes or so that we must have read so
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* far. */
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if (buffer[len-1] == ';') {
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printk (KERN_DEBUG "%s: Device ID reading stopped"
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" before device told data not available. "
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"Current idlen %d of %d, len bytes %02X %02X\n",
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port->name, current_idlen, numidlens,
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length[0], length[1]);
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goto done;
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}
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}
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if (current_idlen < numidlens) {
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/* Buffer not large enough, read to end of buffer. */
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size_t idlen, len2;
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if (len+1 < count) {
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retval = parport_read (port, buffer+len, count-len-1);
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if (retval < 0)
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return retval;
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len += retval;
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}
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/* Read the whole ID since some devices would not
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* otherwise give back the Device ID from beginning
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* next time when asked. */
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idlen = idlens[current_idlen];
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len2 = len;
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while(len2 < idlen && retval > 0) {
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char tmp[4];
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retval = parport_read (port, tmp,
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min(sizeof tmp, idlen-len2));
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if (retval < 0)
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return retval;
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len2 += retval;
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}
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}
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/* In addition, there are broken devices out there that don't
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even finish off with a semi-colon. We do not need to care
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about those at this time. */
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done:
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buffer[len] = '\0';
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return len;
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}
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/* Get Std 1284 Device ID. */
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ssize_t parport_device_id (int devnum, char *buffer, size_t len)
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ssize_t parport_device_id (int devnum, char *buffer, size_t count)
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{
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ssize_t retval = -ENXIO;
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struct pardevice *dev = parport_open (devnum, "Device ID probe",
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@ -139,76 +262,20 @@ ssize_t parport_device_id (int devnum, char *buffer, size_t len)
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parport_claim_or_block (dev);
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/* Negotiate to compatibility mode, and then to device ID mode.
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* (This is in case we are already in device ID mode.) */
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/* Negotiate to compatibility mode, and then to device ID
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* mode. (This so that we start form beginning of device ID if
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* already in device ID mode.) */
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parport_negotiate (dev->port, IEEE1284_MODE_COMPAT);
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retval = parport_negotiate (dev->port,
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IEEE1284_MODE_NIBBLE | IEEE1284_DEVICEID);
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if (!retval) {
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int idlen;
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unsigned char length[2];
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/* First two bytes are MSB,LSB of inclusive length. */
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retval = parport_read (dev->port, length, 2);
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if (retval != 2) goto end_id;
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idlen = (length[0] << 8) + length[1] - 2;
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/*
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* Check if the caller-allocated buffer is large enough
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* otherwise bail out or there will be an at least off by one.
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*/
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if (idlen + 1 < len)
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len = idlen;
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else {
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retval = -EINVAL;
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goto out;
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}
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retval = parport_read (dev->port, buffer, len);
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if (retval != len)
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printk (KERN_DEBUG "%s: only read %Zd of %Zd ID bytes\n",
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dev->port->name, retval,
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len);
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/* Some printer manufacturers mistakenly believe that
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the length field is supposed to be _exclusive_.
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In addition, there are broken devices out there
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that don't even finish off with a semi-colon. */
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if (buffer[len - 1] != ';') {
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ssize_t diff;
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diff = parport_read (dev->port, buffer + len, 2);
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retval += diff;
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if (diff)
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printk (KERN_DEBUG
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"%s: device reported incorrect "
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"length field (%d, should be %Zd)\n",
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dev->port->name, idlen, retval);
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else {
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/* One semi-colon short of a device ID. */
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buffer[len++] = ';';
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printk (KERN_DEBUG "%s: faking semi-colon\n",
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dev->port->name);
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/* If we get here, I don't think we
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need to worry about the possible
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standard violation of having read
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more than we were told to. The
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device is non-compliant anyhow. */
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}
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}
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end_id:
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buffer[len] = '\0';
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retval = parport_read_device_id (dev->port, buffer, count);
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parport_negotiate (dev->port, IEEE1284_MODE_COMPAT);
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if (retval > 2)
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parse_data (dev->port, dev->daisy, buffer+2);
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}
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if (retval > 2)
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parse_data (dev->port, dev->daisy, buffer);
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out:
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parport_release (dev);
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parport_close (dev);
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return retval;
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