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SubjectRe: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking
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> On Fri, Nov 19, 2010 at 11:19 AM, Sarah Sharp
> <sarah.a.sharp@linux.intel.com> wrote:
> >
> > .config and dmesg are attached. The box is running klogd 1.5.5ubuntu3
> > (from Jaunty). Yes, I know that's old. I read the bit in the commit
> > about changing the permissions of kallsyms after boot, but if I can't
> > boot that doesn't help. Perhaps this can be made a configuration
> > option?
>
> It's not worth a config option.
>
> If it actually breaks user-space, I think we should just revert it.

User space klogd is what's broken in this case:

ksyms = fopen(KSYMS, "r");

if ( ksyms == NULL )
{
if ( errno == ENOENT )
Syslog(LOG_INFO, "No module symbols loaded - "
"kernel modules not enabled.\n");
else
Syslog(LOG_ERR, "Error loading kernel symbols " \
"- %s\n", strerror(errno));
fclose(ksyms);
return(0);
}

The fclose(NULL) is a bug, as I don't think the standards require
that to be handled gracefully.


> It's kind of sad to default to the world-visible thing,

klogd also gets symbols from System.map, so /proc/kallsyms access
is not a strict requirement.

I haven't checked to see if klogd can work without a symbol source
at all, but I'll wager it can.

Regards,
Andy




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