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SubjectRe: [PATCH] param: fixup quote parsing of kernel arguments
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Arthur Gautier <baloo@gandi.net> writes:
> On Wed, Apr 08, 2015 at 03:29:43PM +0930, Rusty Russell wrote:
>> Arthur Gautier <baloo@gandi.net> writes:
>> > When starting kernel with arguments like:
>> > init=/bin/sh -c "echo arguments"
>> > the trailing double quote is not removed which results in following command
>> > being executed:
>> > /bin/sh -c 'echo arguments"'
>> >
>> > This commit removes the trailing double quote.
>> >
>> > Signed-off-by: Arthur Gautier <baloo@gandi.net>
>>
>> Hi Arthur,
>>
>> Thanks, I'd not considered quotes outside '='. But this
>> fixes it in a weird way: we handle quotes below, we just don't do
>> anything for the "raw value" case:
>>
>> for (i = 0; args[i]; i++) {
>> if (isspace(args[i]) && !in_quote)
>> break;
>> if (equals == 0) {
>> if (args[i] == '=')
>> equals = i;
>> }
>> if (args[i] == '"')
>> in_quote = !in_quote;
>> }
>>
>> *param = args;
>> if (!equals)
>> *val = NULL;
>> else {
>> args[equals] = '\0';
>> *val = args + equals + 1;
>>
>> /* Don't include quotes in value. */
>> if (**val == '"') {
>> (*val)++;
>> if (args[i-1] == '"')
>> args[i-1] = '\0';
>> }
>> if (quoted && args[i-1] == '"')
>> args[i-1] = '\0';
>> }
>>
>> The logical fix is to just always remove the close quotes in both
>> cases:
>>
>> diff --git a/kernel/params.c b/kernel/params.c
>> index 728e05b167de..a22d6a759b1a 100644
>> --- a/kernel/params.c
>> +++ b/kernel/params.c
>> @@ -173,9 +173,9 @@ static char *next_arg(char *args, char **param, char **val)
>> if (args[i-1] == '"')
>> args[i-1] = '\0';
>> }
>> - if (quoted && args[i-1] == '"')
>> - args[i-1] = '\0';
>> }
>> + if (quoted && args[i-1] == '"')
>> + args[i-1] = '\0';
>>
>> if (args[i]) {
>> args[i] = '\0';
>>
>> Does this work for you?
>>
>
> Hi Rusty,
>
> This does indeed fixes my issue and I agree with the fix but I've also
> noticed a problem when parsing commands like:
>
> char * input = "var0=\"val=ue\" \"var1\"=value \"var2=value\" \"echo foo\"";
> char buf[255];
> char *args = buf;
> char * param, *val;
>
> memcpy(buf, input, strlen(input)+1);
>
> while(*args)
> {
> args = next_arg(args, &param, &val);
> printf("%s=%s\n", param, val);
> }
>
> This parses commandline like:
>
> var0=val=ue
> var1"=value
> var2=value
> echo foo=(null)
>
> As you may notice when using doublequote for keys, the final doublequote
> is not removed. I'm not sure this should be considered as a problem nor
> this should be expected but my patch was fixing this issue as well.

Indeed. And the following isn't parse correctly either:

foo="one ""two"

Though it *looks* like the code handles this, it doesn't: you'll get
'one ""two'.

Your first case was interesting because it was a more practical example.

I've applied my simple fix for now; if you want to do more thorough quote
handling (ie. use memmove), I'd love to see patches.

Thanks!
Rusty.


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