Description of problem:

When grub.cfg contains special characters like &, $, etc., grub2 treats them like metacharacters and gives them special meaning. This is - in some cases - unwanted in the case of a kernel command line.

The grub documentation [1], section 5.2, mentions that

  "Enclosing characters in single quotes preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash."

This means that pre-processing the kernel command line by enclosing it in single quotes and escaping any existing single quotes should make grub pass the cmdline unchanged, without interpreting it as special.

For example:

  lorem ipsum&dolor$sit'amet"

would be specified as

  'lorem ipsum&dolor$sit'\''amet"'

However this instead becomes, when "cat /proc/cmdline" on a running system,

  "lorem ipsum&dolor$sit\'amet\""

Turning it into multiple arguments for the linux/linux16 command by using a variable,

  set testvar='lorem ipsum&dolor$sit'\''amet"'
  linux16 /some/image ... $testvar

gets rid of the double quotes (which are a valid operation by the linux/linux16 command), but still manages to overquote / overescape the result:

  lorem ipsum&dolor$sit\'amet\"


[1]: http://www.gnu.org/software/grub/manual/html_node/Shell_002dlike-scripting.html#Shell_002dlike-scripting


Version-Release number of selected component (if applicable):
grub2-2.02-0.16.el7.x86_64

How reproducible:
always

Actual results:
grub overescapes the input on (at least) linux/linux16 command lines

Expected results:
grub behaves according to docs, without treating anything inside '' as special

Additional info:
This issue was somewhat discussed upstream, http://lists.gnu.org/archive/html/help-grub/2015-06/msg00004.html .

There's a potential customer impact if the customer uses ie. PHP/CGI to generate a parametrized kickstart, passing it as ks= on the cmdline. For example ks=http://host/ks.cfg?param1=value1&param2=value2 . This worked fine with grub1 (on RHEL6) and syslinux (pxelinux), but doesn't with grub2 (important for UEFI and RHEL7).