Re: [PATCH] parser: Remove escape from the state transitions

[Eric Snowberg]

> On Jun 7, 2017, at 1:23 PM, Daniel Kiper <address@hidden> wrote:
> 
> On Mon, Jun 05, 2017 at 08:29:47AM -0600, Eric Snowberg wrote:
>>> On Jun 2, 2017, at 4:41 AM, Daniel Kiper <address@hidden> wrote:
>>> On Tue, May 30, 2017 at 04:07:52PM -0600, Eric Snowberg wrote:
>>>> Remove GRUB_PARSER_STATE_ESC with state GRUB_PARSER_STATE_TEXT from
>>>> the list of not allowed characters.
>>>> 
>>>> This fixes a problem where a properly escaped comma is in the disk path.
>>>> 
>>>> For example: 
>>>> /address@hidden/address@hidden/LSI,address@hidden/address@hidden:a
>>>> 
>>>> During grub install, the search.fs_uuid is correctly stored in the
>>>> core.img.
>>>> 
>>>> As seen here:
>>>> 
>>>> 001e380: 7365 6172 6368 2e66 735f 7575 6964 2039  search.fs_uuid 9
>>>> 001e390: 6462 6137 6333 362d 6431 6432 2d34 6163  dba7c36-d1d2-4ac
>>>> 001e3a0: 642d 6135 3037 2d30 3634 6132 3462 3538  d-a507-064a24b58
>>>> 001e3b0: 3666 3420 726f 6f74 2069 6565 6531 3237  6f4 root ieee127
>>>> 001e3c0: 352f 2f70 6369 4033 3036 2f70 6369 4031  
>>>> 5//address@hidden/address@hidden
>>>> 001e3d0: 2f4c 5349 5c2c 6d72 7361 7340 302f 6469  /LSI\,address@hidden/di
>>>> 001e3e0: 736b 4030 3a61 200a 7365 7420 7072 6566  address@hidden:a .set 
>>>> pref
>>>> 001e3f0: 6978 3d28 2472 6f6f 7429 272f 6772 7562  ix=($root)'/grub
>>>> 001e400: 3227 0a00 0000 0000 0000 0003 0000 0010  2'..............
>>>> 001e410: 2f67 7275 6232 0000                      /grub2..
>>>> 
>>>> Before this change the following args would be sent to
>>>> grub_cmd_do_search:
>>>> 
>>>> key: 9dba7c36-d1d2-4acd-a507-064a24b586f4
>>>> var: root
>>>> hint: 
>>>> ieee1275//address@hidden/address@hidden/LSI,address@hidden/address@hidden:a
>>>> 
>>>> The hint above is not correct.  It should be:
>>>> 
>>>> hint: 
>>>> ieee1275//address@hidden/address@hidden/LSI\,address@hidden/address@hidden:a
>>>> 
>>>> Later on, when it tries to use this disk, it incorrectly truncates
>>>> the device name since the comma isn’t escaped and tries to do the
>>>> grub_disk_open with ieee1275//address@hidden/address@hidden/LSI.
>>>> 
>>>> Signed-off-by: Eric Snowberg <address@hidden>
>>>> ---
>>>> grub-core/kern/parser.c |    1 -
>>>> 1 files changed, 0 insertions(+), 1 deletions(-)
>>>> 
>>>> diff --git a/grub-core/kern/parser.c b/grub-core/kern/parser.c
>>>> index 78175aa..be88baa 100644
>>>> --- a/grub-core/kern/parser.c
>>>> +++ b/grub-core/kern/parser.c
>>>> @@ -30,7 +30,6 @@ static struct grub_parser_state_transition 
>>>> state_transitions[] = {
>>>>  {GRUB_PARSER_STATE_TEXT, GRUB_PARSER_STATE_QUOTE, '\'', 0},
>>>>  {GRUB_PARSER_STATE_TEXT, GRUB_PARSER_STATE_DQUOTE, '\"', 0},
>>>>  {GRUB_PARSER_STATE_TEXT, GRUB_PARSER_STATE_VAR, '$', 0},
>>>> -  {GRUB_PARSER_STATE_TEXT, GRUB_PARSER_STATE_ESC, '\\', 0},
>>> 
>>> I have a feeling that this way you break parser for everybody.
>> 
>> Can you explain what would break on other platforms with this change?
> 
> After your patch embedded config is parsed incorrectly, e.g. "set a=\f"
> sets $a to "\f" instead of "f”.

That is a useful config?

> 
>>> Could you explain why it is valid for all?
>> 
>> Any platform containing a device with a comma in it would have the
>> problem I identified above.
> 
> So, I think that you should store unescaped strings in core.img if it is 
> required.

Throughout GRUB a comma is escaped unless it is before a partition number. If I 
store it unescaped in the core.img I would still have the same problem above 
when going into grub_disk_open.