libkmod mishandles parameters re-quoted by grub2

Hi,

when one passes to the kernel a module parameter from grub2 such as:
  parport.dyndbg="file drivers/parport/ieee1284_ops.c +mpf"
the kernel receives:
  "parport.dyndbg=file drivers/parport/ieee1284_ops.c +mpf"
as grub2 handles quotes this way. It may be a bug in grub2, it was even tried to be fixed, but there is no all-cases-working fix yet:
  https://bugzilla.suse.com/show_bug.cgi?id=1181111#c10

The kernel parses the parameter correctly, though:
  parse_one: doing dyndbg params: parport.dyndbg='file drivers/parport/ieee1284_ops.c +mpf'

But libkmod doesn't. When parport is modprobe-d, this parameter is not passed to it.

kmod_config_parse_kcmdline ignores the parameter as:
  if (is_quoted) {
    /* don't consider a module until closing quotes */

I am not sure how to fix this, can someone look into it and make the parser similar to kernel's?

thanks,
-- 
js
suse labs

On Mon, Jan 25, 2021 at 10:06 PM Jiri Slaby [off-list ref] wrote:

Hi,

when one passes to the kernel a module parameter from grub2 such as:
   parport.dyndbg="file drivers/parport/ieee1284_ops.c +mpf"
the kernel receives:
   "parport.dyndbg=file drivers/parport/ieee1284_ops.c +mpf"
as grub2 handles quotes this way. It may be a bug in grub2, it was even
tried to be fixed, but there is no all-cases-working fix yet:
   https://bugzilla.suse.com/show_bug.cgi?id=1181111#c10

The kernel parses the parameter correctly, though:
   parse_one: doing dyndbg params: parport.dyndbg='file
drivers/parport/ieee1284_ops.c +mpf'

But libkmod doesn't. When parport is modprobe-d, this parameter is not
passed to it.

yeah... if kernel parses the parameter correctly, we should accept it too.

kmod_config_parse_kcmdline ignores the parameter as:
   if (is_quoted) {
     /* don't consider a module until closing quotes */

I am not sure how to fix this, can someone look into it and make the
parser similar to kernel's?

I will take a look soon.

thanks
Lucas De Marchi

thanks,
--
js
suse labs

On Mon, Jan 25, 2021 at 09:49:13AM +0100, Jiri Slaby wrote:

Hi,

when one passes to the kernel a module parameter from grub2 such as:
 parport.dyndbg="file drivers/parport/ieee1284_ops.c +mpf"
the kernel receives:
 "parport.dyndbg=file drivers/parport/ieee1284_ops.c +mpf"
as grub2 handles quotes this way. It may be a bug in grub2, it was even tried to be fixed, but there is no all-cases-working fix yet:
 https://bugzilla.suse.com/show_bug.cgi?id=1181111#c10

The kernel parses the parameter correctly, though:
 parse_one: doing dyndbg params: parport.dyndbg='file drivers/parport/ieee1284_ops.c +mpf'

But libkmod doesn't. When parport is modprobe-d, this parameter is not passed to it.

kmod_config_parse_kcmdline ignores the parameter as:
 if (is_quoted) {
   /* don't consider a module until closing quotes */

I am not sure how to fix this, can someone look into it and make the parser similar to kernel's?

We have to ignore ill-formed kernel cmdline and that makes it harder.

I threw out the current implementation and rewrote it into a state
machine. It passes the tests, but it's unfortunate we have to do this,
particularly because we have to re-quote it the "right way" to pass back
to kernel, unmangling it.

I will share the patch shortly.

Lucas De Marchi

thanks,
-- 
js
suse labs