printer-driver.c: Fix crash when adding generic PS printer #322
Conversation
If legacy-printer-app is run for the first time and generic PS driver was chosen when installing the printer, the application crashes during adding the printer. It is because the printer structure does not have device_id set, and the library tries to get data from already freed `printer->driver_attrs`. Additionally, if the device id exists in the printer, it rewrites incorrect structure (we should set device id attr in `attrs`, which we return). The fix adds possibility to extract device id from `printer->attrs` and if device id is missing in `printer->attrs` and `document-format-supported` as well, try `document-format-default` and if this attribute is missing, return NULL.
|
The key for reproducing the issue is that it must be the first run of legacy-printer-app after its installation and start. I was not able to reproduce in other runs. |
|
Hard to diagnose this without a backtrace... |
|
Full backtrace of the crash - the program crashes in libcups, because it tries to access invalid memory, which was freed in pappl, however it is accessed later during generating driver attributes. It is the thread 1, in ippFindNextAttribute() function. |
| ippAddString(printer->attrs, IPP_TAG_PRINTER, IPP_TAG_TEXT, "printer-device-id", NULL, printer->device_id); | ||
| ippAddString(attrs, IPP_TAG_PRINTER, IPP_TAG_TEXT, "printer-device-id", NULL, printer->device_id); | ||
| } | ||
| else if ((attr = ippFindAttribute(printer->attrs, "printer-device-id", IPP_TAG_PRINTER)) != NULL) |
There was a problem hiding this comment.
After looking through this, we don't want to look for printer-device-id in printer->attrs since it shouldn't be there and you'd end up with duplicate printer-device-id attrs.
| @@ -986,7 +990,10 @@ make_attrs( | |||
| else | |||
| mdl = mfg; // No separator, so assume the make and model are the same | |||
|
|
|||
| formats = ippFindAttribute(printer->driver_attrs, "document-format-supported", IPP_TAG_MIMETYPE); | |||
| if ((formats = ippFindAttribute(printer->attrs, "document-format-supported", IPP_TAG_MIMETYPE)) == NULL) | |||
There was a problem hiding this comment.
This should just be looking in attrs since printer->attrs won't have document-format-supported (driver-specific) and we just want document-format-supported since document-format-default is just the one default and usually application/octet-stream.
|
Thank you for the fix, Mike! It works in my testing env. |
If legacy-printer-app is run for the first time and generic PS driver was chosen when installing the printer, the application crashes during adding the printer.
It is because the printer structure does not have device_id set, and the library tries to get data from already freed
printer->driver_attrs. Additionally, if the device id exists in the printer, it rewrites incorrect structure (we should set device id attr inattrs, which we return).The fix adds possibility to extract device id from
printer->attrsand if device id is missing inprinter->attrsanddocument-format-supportedas well, trydocument-format-defaultand if this attribute is missing, return NULL.