Re: [PATCH] Open Firmware device tree virtual filesystem

Mitch Bradley
2006-12-31T18:55:40Z

I made all the changes Pekka suggested, except:

> + security = strncmp(propname, "security-", 9) == 0;
>> + len = 0;
>
> Redundant assignment, no?
>
>> + if (!security)
>> + (void)callofw("getproplen", 2, 1, node,
>> propname, &len);
>
That assignment turns out not to be redundant. If a security variable
is recognized, you want the length to be 0 so as not to expose the
password. In that case the following "getproplen" call won't be executed.

That logic was adapted from the existing file fs/proc/devtree.c . It
turns out that the code there has a bug: You really want to look for
just "security-password" ; there is no need to, and good reasons not to,
suppress the length of "security-mode" and "security-#badlogins". (Good
OFW implementations won't leak the password length anyway, so check is
only needed as a workaround).

I have rewritten the code for clarity and correctness thusly:

if (strcmp(propname, "security-password") == 0) {
len = 0; /* Don't leak password length */
} else {
callofw("getproplen", 2, 1, node, propname, &len);
}